Skip DB registration in standalone mode (fixes sx-web.org startup)

The sx app is stateless — no database needed. In standalone mode
(SX_STANDALONE=true), the factory now skips register_db() so the app
doesn't crash trying to connect to a non-existent PostgreSQL.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/infrastructure/factory.py

@@ -48,6 +48,7 @@ def create_base_app(
     before_request_fns: Sequence[Callable[[], Awaitable[None]]] | None = None,
     domain_services_fn: Callable[[], None] | None = None,
     no_oauth: bool = False,
+    no_db: bool = False,
 ) -> Quart:
     """
     Create a Quart app with shared infrastructure.
@@ -111,7 +112,8 @@ def create_base_app(
 
     # --- infrastructure ---
     register_middleware(app)
-    register_db(app)
+    if not no_db:
+        register_db(app)
     register_redis(app)
     setup_jinja(app)
     setup_sx_bridge(app)

sx/app.py

@@ -58,6 +58,7 @@ def create_app() -> "Quart":
     extra_kw = {}
     if SX_STANDALONE:
         extra_kw["no_oauth"] = True
+        extra_kw["no_db"] = True
 
     app = create_base_app(
         "sx",