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/browse/routes.py

@@ -10,7 +10,7 @@ from quart import (
     make_response,
     current_app,
 )
-from config import config
+from shared.config import config
 from .services.nav import category_context, get_nav
 from .services.blacklist.category import is_category_blocked
 
@@ -21,8 +21,8 @@ from .services import (
   _current_url_without_page,
 )
 
-from suma_browser.app.redis_cacher import cache_page
-from suma_browser.app.utils.htmx import is_htmx_request
+from shared.browser.app.redis_cacher import cache_page
+from shared.browser.app.utils.htmx import is_htmx_request
 
 def register():
   browse_bp = Blueprint("browse", __name__)