feat: P0-P4 Infrastructure & Documentation Completion (AGENTS.md v16.0)

**P0: DB Isolation** ✅ VERIFIED
- Test appsettings.Development.json uses kartselldb_test (isolated)
- 135/135 tests passing against kartselldb_test

**P1: Gate 3 Data Layer Real Integration** ✅ COMPLETE
- KrxDataService (real) registered in Program.cs
- Fallback to stub data if KRX_API_KEY missing
- No breaking changes to existing code

**P2: Observability Service Integration** ✅ COMPLETE
- ObservabilityService (real) registered in Program.cs
- MetricsSql queries (PIT-based) connected
- Dashboard ready for Gate 3 metrics

**P3: MetricsSql Placeholder Cleanup** ✅ COMPLETE
- GetDuplicateDetectionAsync: Clarified audit trail dependency
- GetReconciliationBreaksAsync: Explained version mismatch correlation need
- GetModelDriftAsync: Documented Gate 3 runnable prerequisite

**P4: Documentation Updates** ✅ COMPLETE
- CURRENT_ROADMAP.md: Gate 3 IN PROGRESS status, real execution steps
- PRODUCTION_READINESS.md: 135/135 tests, 78% ready, Gate 3 rehearsal active
- TECH_DEBT_REGISTER.md: Added DEBT-015 (Hangfire lock resilience)

**Infrastructure Status**
- ✅ Host running (Development mode, port 5002)
- ✅ SSH tunnel active (remote PostgreSQL)
- ✅ Hangfire Job 269 executing (Phase 1-5 in progress)
- ✅ Gate 3 Shadow Run ID: d14f34ea-2afe-4caf-bbb1-c9a7d74fb582
- ⏳ Model operations.shadow_run write pending (Job completion)

**Test Coverage**: 135/135 PASS (5 arch + 95 integration + 35 unit)

**Next**: Gate 3 completion monitoring + P5 tech debt documentation

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

TECH_DEBT_REGISTER.md

@@ -8,7 +8,7 @@
 
 | Status | Count | Total Impact |
 |--------|-------|--------------|
-| Backlog | 6 | 12 pts |
+| Backlog | 7 | 14 pts |
 | In Progress | 0 | 0 pts |
 | Completed | 1 | 1 pt |
 | No Action | 1 | 1 pt |
@@ -40,6 +40,7 @@
 | DEBT-012 | False-exit analysis | High (3) | High (3) | Backlog | ShadowRunJob.cs:136-139, FalseExitAnalyzer.cs always returns 0. Unimplemented feature. Required for accurate sell-reason attribution. Gate 3 rehearsal does not include false-exit analysis; deferred to separate work. | @claude | Gate 3 Rehearsal Scope |
 | DEBT-013 | Credentials in appsettings | High (3) | Low (1) | Backlog | Host/tests appsettings.json contains plaintext DB password (kartsell4321@!). Must migrate to Gitea Actions Secrets and environment variables. Security compliance required. | @claude | Security / Ops |
 | DEBT-014 | Duplicate & reconciliation tracking | Medium (2) | Medium (2) | Backlog | MetricsSql.cs GetDuplicateDetectionAsync/GetReconciliationBreaksAsync return null placeholders. Requires operation_audit_trail population by job consumers + OutboxPollerJob hooks. Non-blocking; dashboard degrades gracefully. | @claude | Observability Enhancement |
+| DEBT-015 | Hangfire distributed lock timeout resilience | Medium (2) | High (3) | Backlog | Program.cs:224-238 wraps recurring job registration in try/catch to handle stuck locks (silent failure). Masks root cause of contention: multiple Host instances, network timeouts, or genuine lock stuck states. Proper fix requires distributed lock diagnostics + single-instance enforcement or timeout tuning. | @claude | Host Reliability |
 
 ### Deferred Refactoring