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/market/admin/routes.py

@@ -5,7 +5,7 @@ from quart import (
 )
 
 
-from suma_browser.app.authz import require_admin
+from shared.browser.app.authz import require_admin
 
 
 def register():
@@ -15,7 +15,7 @@ def register():
     @bp.get("/")
     @require_admin
     async def admin():
-        from suma_browser.app.utils.htmx import is_htmx_request
+        from shared.browser.app.utils.htmx import is_htmx_request
 
         # Determine which template to use based on request type
         if not is_htmx_request():

bp/market/filters/qs.py

@@ -2,10 +2,10 @@ from quart import request
 
 from typing import Iterable, Optional, Union
 
-from suma_browser.app.filters.qs_base import (
+from shared.browser.app.filters.qs_base import (
     KEEP, _norm, make_filter_set, build_qs,
 )
-from suma_browser.app.filters.query_types import MarketQuery
+from shared.browser.app.filters.query_types import MarketQuery
 
 
 def decode() -> MarketQuery: