feat: add proper Pydantic response_model to all stats endpoints

- Create comprehensive stats schemas in models/schema/stats.py:
  - ImportStatsResponse, UserStatsResponse, ProductStatsResponse
  - PlatformStatsResponse, AdminDashboardResponse
  - VendorDashboardStatsResponse with nested models
  - VendorAnalyticsResponse, CodeQualityDashboardStatsResponse
- Move DashboardStatsResponse from code_quality.py to schema file
- Fix get_vendor_statistics() to return pending_vendors field
- Fix get_vendor_stats() to return flat structure matching schema
- Add response_model to all stats endpoints:
  - GET /admin/dashboard -> AdminDashboardResponse
  - GET /admin/dashboard/stats/platform -> PlatformStatsResponse
  - GET /admin/marketplace-import-jobs/stats -> ImportStatsResponse
  - GET /vendor/dashboard/stats -> VendorDashboardStatsResponse
  - GET /vendor/analytics -> VendorAnalyticsResponse
- Enhance API-001 architecture rule with detailed guidance
- Add SVC-007 rule for service/schema compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/api/v1/admin/code_quality.py

@@ -14,6 +14,7 @@ from app.core.database import get_db
 from app.exceptions import ViolationNotFoundException
 from app.services.code_quality_service import code_quality_service
 from models.database.user import User
+from models.schema.stats import CodeQualityDashboardStatsResponse
 
 router = APIRouter()
 
@@ -107,25 +108,6 @@ class AddCommentRequest(BaseModel):
     comment: str = Field(..., min_length=1, description="Comment text")
 
 
-class DashboardStatsResponse(BaseModel):
-    """Response model for dashboard statistics"""
-
-    total_violations: int
-    errors: int
-    warnings: int
-    open: int
-    assigned: int
-    resolved: int
-    ignored: int
-    technical_debt_score: int
-    trend: list
-    by_severity: dict
-    by_rule: dict
-    by_module: dict
-    top_files: list
-    last_scan: str | None = None
-
-
 # API Endpoints
 
 
@@ -447,7 +429,7 @@ async def add_comment(
     }
 
 
-@router.get("/stats", response_model=DashboardStatsResponse)
+@router.get("/stats", response_model=CodeQualityDashboardStatsResponse)
 async def get_dashboard_stats(
     db: Session = Depends(get_db), current_user: User = Depends(get_current_admin_api)
 ):
@@ -463,4 +445,4 @@ async def get_dashboard_stats(
     """
     stats = code_quality_service.get_dashboard_stats(db)
 
-    return DashboardStatsResponse(**stats)
+    return CodeQualityDashboardStatsResponse(**stats)