chore: PostgreSQL migration compatibility and infrastructure improvements

Database & Migrations:
- Update all Alembic migrations for PostgreSQL compatibility
- Remove SQLite-specific syntax (AUTOINCREMENT, etc.)
- Add database utility helpers for PostgreSQL operations
- Fix services to use PostgreSQL-compatible queries

Documentation:
- Add comprehensive Docker deployment guide
- Add production deployment documentation
- Add infrastructure architecture documentation
- Update database setup guide for PostgreSQL-only
- Expand troubleshooting guide

Architecture & Validation:
- Add migration.yaml rules for SQL compatibility checking
- Enhance validate_architecture.py with migration validation
- Update architecture rules to validate Alembic migrations

Development:
- Fix duplicate install-all target in Makefile
- Add Celery/Redis validation to install.py script
- Add docker-compose.test.yml for CI testing
- Add squash_migrations.py utility script
- Update tests for PostgreSQL compatibility
- Improve test fixtures in conftest.py

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

app/services/email_service.py

@@ -1012,10 +1012,12 @@ class EmailService:
     def _has_feature(self, vendor_id: int, feature_code: str) -> bool:
         """Check if vendor has a specific feature enabled."""
         if vendor_id not in self._feature_cache:
-            from app.core.feature_gate import get_vendor_features
+            from app.services.feature_service import feature_service
 
             try:
-                self._feature_cache[vendor_id] = get_vendor_features(self.db, vendor_id)
+                features = feature_service.get_vendor_features(self.db, vendor_id)
+                # Convert to set of feature codes
+                self._feature_cache[vendor_id] = {f.code for f in features.features}
             except Exception:
                 self._feature_cache[vendor_id] = set()
 
@@ -1161,10 +1163,10 @@ class EmailService:
             # Whitelabel: use vendor branding throughout
             return BrandingContext(
                 platform_name=vendor.name,
-                platform_logo_url=vendor.logo_url,
+                platform_logo_url=vendor.get_logo_url(),
                 support_email=vendor.support_email or PLATFORM_SUPPORT_EMAIL,
                 vendor_name=vendor.name,
-                vendor_logo_url=vendor.logo_url,
+                vendor_logo_url=vendor.get_logo_url(),
                 is_whitelabel=True,
             )
         else:
@@ -1174,7 +1176,7 @@ class EmailService:
                 platform_logo_url=None,  # Use default platform logo
                 support_email=PLATFORM_SUPPORT_EMAIL,
                 vendor_name=vendor.name if vendor else None,
-                vendor_logo_url=vendor.logo_url if vendor else None,
+                vendor_logo_url=vendor.get_logo_url() if vendor else None,
                 is_whitelabel=False,
             )