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/tests/test_product_model.py

@@ -1,6 +1,8 @@
 """Unit tests for Product.to_llm_context() — no database required."""
 from uuid import uuid4
 
+from typing import Any
+
 import pytest
 
 from innercontext.models import Product
@@ -18,8 +20,8 @@ from innercontext.models.product import (
 )
 
 
-def _make(**kwargs):
-    defaults = dict(
+def _make(**kwargs: Any) -> Product:
+    defaults: dict[str, Any] = dict(
         id=uuid4(),
         name="Test",
         brand="B",