refactor: move buildable .NET source into src/, update CI/doc paths

Groups the repo root into src (buildable source), docs (already existed),
and everything else (db/, scripts/, tests/, deploy/ - deployment/ops/test
assets that aren't compiled, already organized as their own folders). CI
now only needs src/ to build: dotnet restore/build/test/publish all point
at src/TaxBaik.sln, src/TaxBaik.Web/, src/TaxBaik.Proxy/.

- git mv every project (Domain, Infrastructure, Application,
  Application.Tests, Web, Web.Client, Proxy) and TaxBaik.sln into src/ as a
  unit, so relative ProjectReference/.sln paths stay valid unchanged.
- .gitea/workflows/deploy.yml: 6 dotnet restore/clean/build/test/publish
  invocations now point at src/. db/migrations and scripts/ stay at root
  (deploy_gb.sh and browser-e2e.yml only touch published output and the
  deployed URL, not source paths - verified, no changes needed there).
- scripts/validate_admin_render.sh: admin render-mode file paths now
  src/TaxBaik.Web.Client/...
- scripts/validate_kst_timestamps.sh: dropped deploy.sh from its target
  list - that script was removed in the prior cleanup commit (dead, no
  CI workflow referenced it) but this validator still expected it to exist.
- CLAUDE.md, docs/ENGINEERING_HARNESS.md, docs/ADMIN_PATTERN_CRITIQUE_WBS.md:
  updated project-structure diagram, dotnet run/build commands, and grep
  targets to the new src/ paths (also fixed a pre-existing stale path in
  ADMIN_PATTERN_CRITIQUE_WBS.md that still said TaxBaik.Web/Components/Admin
  from before that ever moved to TaxBaik.Web.Client).
- Added a Repo Root harness rule + Architecture Guardrail entries: new files
  belong under src/docs/tests/scripts/db/deploy, not loose at root; temp
  work stays outside the repo (or under a gitignored .scratch/) and is
  never committed.

Verified locally: dotnet build/test src/TaxBaik.sln (26/26 tests), and all
three scripts/validate_*.sh pass against the new layout.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/TaxBaik.Web.Client/Components/Admin/Pages/Companies/CompanyCreate.razor

@@ -0,0 +1,52 @@
+@page "/admin/companies/create"
+@rendermode @(new InteractiveWebAssemblyRenderMode(prerender: false))
+@attribute [Authorize]
+@using TaxBaik.WasmClient.Components.Admin.Forms
+@inject IApiClient ApiClient
+@inject NavigationManager Navigation
+@inject ISnackbar Snackbar
+
+<PageTitle>고객사 등록</PageTitle>
+
+<section class="admin-page-hero">
+    <div>
+        <MudText Typo="Typo.caption" Class="admin-eyebrow">Settings</MudText>
+        <MudText Typo="Typo.h4" Class="admin-page-title">새 고객사 등록</MudText>
+        <MudText Typo="Typo.body2" Class="admin-page-subtitle">새로운 고객사를 추가합니다.</MudText>
+    </div>
+    <MudButton Variant="Variant.Outlined" StartIcon="@Icons.Material.Filled.Close" @onclick="GoBack">취소</MudButton>
+</section>
+
+<MudPaper Class="pa-4 mt-4" Elevation="1">
+    <CompanyForm ButtonText="등록" OnSubmit="HandleCreate" OnCancel="GoBack" />
+</MudPaper>
+
+@code {
+    private void GoBack()
+    {
+        Navigation.NavigateTo("/taxbaik/admin/companies");
+    }
+
+    private async Task HandleCreate(CompanyForm.CompanyFormModel model)
+    {
+        try
+        {
+            await ApiClient.PostAsync<object>("company", new
+            {
+                companyCode = model.CompanyCode,
+                companyName = model.CompanyName,
+                contactPerson = model.ContactPerson,
+                phone = model.Phone,
+                email = model.Email,
+                memo = model.Memo
+            });
+
+            Snackbar.Add("고객사가 등록되었습니다.", Severity.Success);
+            Navigation.NavigateTo("/taxbaik/admin/companies");
+        }
+        catch (Exception ex)
+        {
+            Snackbar.Add($"등록 실패: {ex.Message}", Severity.Error);
+        }
+    }
+}