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

Phase 1-3 of decoupling:
- path_setup.py adds project root to sys.path
- Events-owned models in events/models/ (calendars with all related models)
- All imports updated: shared.infrastructure, shared.db, shared.browser, etc.
- Calendar uses container_type/container_id instead of post_id FK
- CalendarEntryPost uses content_type/content_id (generic content refs)

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

bp/calendar/services/calendar_view.py

@@ -11,7 +11,6 @@ from sqlalchemy.orm import selectinload, with_loader_criteria
 
 from models.calendars import Calendar, CalendarSlot
 
-
 def parse_int_arg(name: str, default: Optional[int] = None) -> Optional[int]:
     """Parse an integer query parameter from the request."""
     val = request.args.get(name, "").strip()
@@ -71,7 +70,8 @@ async def get_calendar_by_post_and_slug(
             with_loader_criteria(CalendarSlot, CalendarSlot.deleted_at.is_(None)),
         )
         .where(
-            Calendar.post_id == post_id,
+            Calendar.container_type == "page",
+            Calendar.container_id == post_id,
             Calendar.slug == calendar_slug,
             Calendar.deleted_at.is_(None),
         )