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/adopt_session_entries_for_user.py

@@ -1,5 +1,6 @@
 from sqlalchemy import select, update
 from models.calendars import CalendarEntry
+
 from sqlalchemy import func
 
 async def adopt_session_entries_for_user(session, user_id: int, session_id: str | None) -> None:

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),
         )

bp/calendar/services/slots.py

@@ -8,6 +8,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from models.calendars import CalendarSlot
 
+
 class SlotError(ValueError):
     pass
 

bp/calendar/services/visiblity.py

@@ -10,6 +10,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from models.calendars import CalendarEntry
 
 
+
 @dataclass
 class VisibleEntries:
     """