add reviews schema and context (phase 2)

- Create reviews table with product/order associations
- Add Review schema with create/update/moderation changesets
- Add Reviews context with CRUD, purchase verification, aggregates
- Add get_images/1 to Media, get_variant/1 to Products
- 23 tests covering all context functions

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

docs/plans/reviews-system.md

@@ -1,6 +1,6 @@
 # Product reviews system
 
-Status: In Progress (Phase 1 complete)
+Status: In Progress (Phase 1-2 complete)
 
 ## Overview
 
@@ -416,13 +416,13 @@ Only include if product has approved reviews.
    - Orders page -> read from email session
    - Checkout success -> set email session (via /checkout/complete controller)
 
-### Phase 2: Reviews schema and context (~2.5h)
+### Phase 2: Reviews schema and context (~2.5h) ✓
 
-3. **Reviews migration and schema** (1h)
+3. **Reviews migration and schema** (1h) ✓
    - Create migration with image_ids array
    - Create `Review` schema with changeset
 
-4. **Reviews context** (1.5h)
+4. **Reviews context** (1.5h) ✓
    - CRUD functions
    - Query helpers (by product, by email, pending)
    - Purchase verification