06/16 Phase 6 foundation: admin blueprint, audit log, user management

Adds the admin backend foundation: AuditLog + Setting models/migration,
an admin-only dashboard with KPI cards, and user management (search,
ban/suspend/activate, tier override, trust adjust) with audit logging
on every write action. Smoke suite extended to 64 checks.

app/models/__init__.py

@@ -9,8 +9,10 @@ from app.models.messaging import Conversation, Message
 from app.models.favorite import Favorite
 from app.models.payments import Subscription, Transaction, Boost
 from app.models.ads import Ad, Sponsor, PromotedKeyword
+from app.models.audit import AuditLog
+from app.models.setting import Setting
 
 __all__ = ["Plan", "User", "TrustEvent", "Category", "Listing",
            "ListingImage", "ZipGeo", "Metro", "Conversation", "Message",
            "Favorite", "Subscription", "Transaction", "Boost",
-           "Ad", "Sponsor", "PromotedKeyword"]
+           "Ad", "Sponsor", "PromotedKeyword", "AuditLog", "Setting"]