feat: decouple market from shared_lib, add app-owned models

Phase 1-3 of decoupling:
- path_setup.py adds project root to sys.path
- Market-owned models in market/models/ (market, market_place)
- All imports updated: shared.infrastructure, shared.db, shared.browser, etc.
- MarketPlace uses container_type/container_id instead of post_id FK

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

bp/product/services/product_operations.py

@@ -13,7 +13,7 @@ def massage_full_product(product: Product) -> dict:
     Convert a Product ORM model to a dictionary with all fields.
     Used for rendering product detail pages.
     """
-    from suma_browser.app.bp.browse.services import _massage_product
+    from bp.browse.services import _massage_product
 
     gallery = []
     if product.image: