refactor: remove personal_rating, DRY get_or_404, fix ty errors

- Drop Product.personal_rating from model, API schemas, and all frontend
  views (list table, detail view, quick-edit form, new-product form)
- Extract get_or_404 into backend/innercontext/api/utils.py; remove five
  duplicate copies from individual API modules
- Fix all ty type errors: generic get_or_404 with TypeVar, cast() in
  coerce_effect_profile validator, col() for ilike on SQLModel column,
  dict[str, Any] annotation in test helper, ty: ignore for CORSMiddleware

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

backend/main.py

@@ -20,7 +20,7 @@ async def lifespan(app: FastAPI):
 app = FastAPI(title="innercontext API", lifespan=lifespan, redirect_slashes=False)
 
 app.add_middleware(
-    CORSMiddleware,
+    CORSMiddleware,  # ty: ignore[invalid-argument-type]
     allow_origins=["*"],
     allow_methods=["*"],
     allow_headers=["*"],