feat: foundation for CRM and tax accounting specialized features

Domain Layer (SOLID Foundation):
- 5 New Entities: TaxProfile, TaxFilingSchedule, ConsultingActivity, Contract, RevenueTracking
- Client entity extended with tax-specific fields
- Multi-tenant support (company_id)

Database Migration (V015):
- Create tax_profiles table for detailed tax info
- Create tax_filing_schedules for deadline tracking
- Create consulting_activities for CRM (activity history)
- Create contracts for contract management
- Create revenue_tracking for invoice and payment tracking
- Add indexes for performance optimization

Repository Interfaces:
- ITaxProfileRepository (tax profile CRUD + risk analysis)
- ITaxFilingScheduleRepository (schedule management + deadline tracking)
- IConsultingActivityRepository (CRM activity tracking)
- IContractRepository (contract lifecycle + MRR calculation)
- IRevenueTrackingRepository (invoice + payment tracking + revenue analysis)

Architecture:
- Follows Repository Pattern with clear separation of concerns
- SOLID principles: each repo = one responsibility
- Extensible design for multi-tenant support
- Supports specialized tax accounting and CRM workflows

TaxBaik.Domain/Entities/Client.cs

@@ -3,15 +3,28 @@ namespace TaxBaik.Domain.Entities;
 public class Client
 {
     public int Id { get; set; }
-    public string Name { get; set; } = null!;
+    public int? CompanyId { get; set; }
+    public string Name { get; set; } = "";
     public string? CompanyName { get; set; }
     public string? Phone { get; set; }
     public string? Email { get; set; }
+    public string? ContactPerson { get; set; }
     public string? ServiceType { get; set; }
     public string? TaxType { get; set; }
     public string Status { get; set; } = "active";
     public string? Source { get; set; }
     public string? Memo { get; set; }
+
+    // Tax-specific fields
+    public string? BusinessRegistrationNumber { get; set; }
+    public string? BusinessType { get; set; }
+    public DateTime? EstablishmentDate { get; set; }
+    public string? AnnualRevenueRange { get; set; }
+    public int? EmployeeCount { get; set; }
+    public DateTime? LastTaxFilingDate { get; set; }
+    public string TaxRiskLevel { get; set; } = "normal";
+    public DateTime? NextFilingDueDate { get; set; }
+
     public DateTime CreatedAt { get; set; }
     public DateTime UpdatedAt { get; set; }
 }

TaxBaik.Domain/Entities/ConsultingActivity.cs

@@ -0,0 +1,17 @@
+namespace TaxBaik.Domain.Entities;
+
+public class ConsultingActivity
+{
+    public int Id { get; set; }
+    public int ClientId { get; set; }
+    public string ActivityType { get; set; } = "";
+    public DateTime ActivityDate { get; set; }
+    public TimeOnly? ActivityTime { get; set; }
+    public int? AssignedConsultantId { get; set; }
+    public string Description { get; set; } = "";
+    public string? Outcome { get; set; }
+    public DateTime? NextFollowupDate { get; set; }
+    public string? Notes { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

TaxBaik.Domain/Entities/Contract.cs

@@ -0,0 +1,19 @@
+namespace TaxBaik.Domain.Entities;
+
+public class Contract
+{
+    public int Id { get; set; }
+    public int ClientId { get; set; }
+    public string ContractNumber { get; set; } = "";
+    public string ServiceType { get; set; } = "";
+    public DateTime ContractDate { get; set; }
+    public DateTime StartDate { get; set; }
+    public DateTime? EndDate { get; set; }
+    public decimal? MonthlyFee { get; set; }
+    public decimal? TotalAmount { get; set; }
+    public string PaymentStatus { get; set; } = "pending";
+    public string Status { get; set; } = "active";
+    public string? Notes { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

TaxBaik.Domain/Entities/RevenueTracking.cs

@@ -0,0 +1,17 @@
+namespace TaxBaik.Domain.Entities;
+
+public class RevenueTracking
+{
+    public int Id { get; set; }
+    public int ClientId { get; set; }
+    public string InvoiceNumber { get; set; } = "";
+    public DateTime InvoiceDate { get; set; }
+    public string? ServiceType { get; set; }
+    public decimal Amount { get; set; }
+    public string PaymentStatus { get; set; } = "pending";
+    public DateTime? PaymentDate { get; set; }
+    public DateTime? DueDate { get; set; }
+    public string? Notes { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

TaxBaik.Domain/Entities/TaxFilingSchedule.cs

@@ -0,0 +1,16 @@
+namespace TaxBaik.Domain.Entities;
+
+public class TaxFilingSchedule
+{
+    public int Id { get; set; }
+    public int ClientId { get; set; }
+    public string FilingType { get; set; } = "";
+    public DateTime DueDate { get; set; }
+    public int FilingYear { get; set; }
+    public string Status { get; set; } = "pending";
+    public int? AssignedToId { get; set; }
+    public DateTime? CompletedDate { get; set; }
+    public string? Notes { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

TaxBaik.Domain/Entities/TaxProfile.cs

@@ -0,0 +1,21 @@
+namespace TaxBaik.Domain.Entities;
+
+public class TaxProfile
+{
+    public int Id { get; set; }
+    public int ClientId { get; set; }
+    public string? BusinessRegistration { get; set; }
+    public string? BusinessType { get; set; }
+    public DateTime? EstablishmentDate { get; set; }
+    public string? AnnualRevenueRange { get; set; }
+    public int? EmployeeCount { get; set; }
+    public string? AccountingMethod { get; set; }
+    public string? FiscalYearEnd { get; set; }
+    public DateTime? LastFilingDate { get; set; }
+    public DateTime? NextFilingDueDate { get; set; }
+    public string TaxRiskLevel { get; set; } = "normal";
+    public bool PreviousAuditHistory { get; set; }
+    public string? SpecialNotes { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

TaxBaik.Domain/Interfaces/IConsultingActivityRepository.cs

@@ -0,0 +1,12 @@
+namespace TaxBaik.Domain.Interfaces;
+
+using TaxBaik.Domain.Entities;
+
+public interface IConsultingActivityRepository
+{
+    Task<int> CreateAsync(ConsultingActivity activity, CancellationToken cancellationToken = default);
+    Task<IEnumerable<ConsultingActivity>> GetByClientIdAsync(int clientId, CancellationToken cancellationToken = default);
+    Task<IEnumerable<ConsultingActivity>> GetPendingFollowupsAsync(CancellationToken cancellationToken = default);
+    Task<IEnumerable<ConsultingActivity>> GetByConsultantAsync(int consultantId, DateTime fromDate, CancellationToken cancellationToken = default);
+    Task UpdateAsync(ConsultingActivity activity, CancellationToken cancellationToken = default);
+}

TaxBaik.Domain/Interfaces/IContractRepository.cs

@@ -0,0 +1,14 @@
+namespace TaxBaik.Domain.Interfaces;
+
+using TaxBaik.Domain.Entities;
+
+public interface IContractRepository
+{
+    Task<int> CreateAsync(Contract contract, CancellationToken cancellationToken = default);
+    Task<Contract?> GetByIdAsync(int id, CancellationToken cancellationToken = default);
+    Task<IEnumerable<Contract>> GetByClientIdAsync(int clientId, CancellationToken cancellationToken = default);
+    Task<IEnumerable<Contract>> GetActiveContractsAsync(CancellationToken cancellationToken = default);
+    Task<IEnumerable<Contract>> GetExpiringContractsAsync(int daysAhead = 30, CancellationToken cancellationToken = default);
+    Task UpdateAsync(Contract contract, CancellationToken cancellationToken = default);
+    Task<decimal> GetMonthlyRecurringRevenueAsync(CancellationToken cancellationToken = default);
+}

TaxBaik.Domain/Interfaces/IRevenueTrackingRepository.cs

@@ -0,0 +1,14 @@
+namespace TaxBaik.Domain.Interfaces;
+
+using TaxBaik.Domain.Entities;
+
+public interface IRevenueTrackingRepository
+{
+    Task<int> CreateAsync(RevenueTracking revenue, CancellationToken cancellationToken = default);
+    Task<IEnumerable<RevenueTracking>> GetByClientIdAsync(int clientId, CancellationToken cancellationToken = default);
+    Task<IEnumerable<RevenueTracking>> GetPendingPaymentsAsync(CancellationToken cancellationToken = default);
+    Task<IEnumerable<RevenueTracking>> GetByDateRangeAsync(DateTime startDate, DateTime endDate, CancellationToken cancellationToken = default);
+    Task UpdateAsync(RevenueTracking revenue, CancellationToken cancellationToken = default);
+    Task MarkPaidAsync(int id, DateTime paymentDate, CancellationToken cancellationToken = default);
+    Task<decimal> GetTotalRevenueAsync(DateTime startDate, DateTime endDate, CancellationToken cancellationToken = default);
+}

TaxBaik.Domain/Interfaces/ITaxFilingScheduleRepository.cs

@@ -0,0 +1,14 @@
+namespace TaxBaik.Domain.Interfaces;
+
+using TaxBaik.Domain.Entities;
+
+public interface ITaxFilingScheduleRepository
+{
+    Task<int> CreateAsync(TaxFilingSchedule schedule, CancellationToken cancellationToken = default);
+    Task<TaxFilingSchedule?> GetByIdAsync(int id, CancellationToken cancellationToken = default);
+    Task<IEnumerable<TaxFilingSchedule>> GetByClientIdAsync(int clientId, CancellationToken cancellationToken = default);
+    Task<IEnumerable<TaxFilingSchedule>> GetUpcomingDuesAsync(int daysAhead = 30, CancellationToken cancellationToken = default);
+    Task<IEnumerable<TaxFilingSchedule>> GetByStatusAsync(string status, CancellationToken cancellationToken = default);
+    Task UpdateAsync(TaxFilingSchedule schedule, CancellationToken cancellationToken = default);
+    Task MarkCompletedAsync(int id, CancellationToken cancellationToken = default);
+}

TaxBaik.Domain/Interfaces/ITaxProfileRepository.cs

@@ -0,0 +1,12 @@
+namespace TaxBaik.Domain.Interfaces;
+
+using TaxBaik.Domain.Entities;
+
+public interface ITaxProfileRepository
+{
+    Task<int> CreateAsync(TaxProfile profile, CancellationToken cancellationToken = default);
+    Task<TaxProfile?> GetByClientIdAsync(int clientId, CancellationToken cancellationToken = default);
+    Task UpdateAsync(TaxProfile profile, CancellationToken cancellationToken = default);
+    Task<IEnumerable<TaxProfile>> GetByRiskLevelAsync(string riskLevel, CancellationToken cancellationToken = default);
+    Task<IEnumerable<TaxProfile>> GetUpcomingFilingDuesAsync(DateTime startDate, DateTime endDate, CancellationToken cancellationToken = default);
+}