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/calendars/routes.py

@@ -7,16 +7,17 @@ from sqlalchemy import select
 
 from models.calendars import Calendar
 
+
 from .services.calendars import (
     create_calendar as svc_create_calendar,
 )
 
 from ..calendar.routes import register as register_calendar
 
-from suma_browser.app.redis_cacher import cache_page, clear_cache
+from shared.browser.app.redis_cacher import cache_page, clear_cache
 
-from suma_browser.app.authz import require_admin
-from suma_browser.app.utils.htmx import is_htmx_request
+from shared.browser.app.authz import require_admin
+from shared.browser.app.utils.htmx import is_htmx_request
 
 
 def register():
@@ -78,7 +79,7 @@ def register():
             cals = (
                 await g.s.execute(
                     select(Calendar)
-                    .where(Calendar.post_id == post_id, Calendar.deleted_at.is_(None))
+                    .where(Calendar.container_type == "page", Calendar.container_id == post_id, Calendar.deleted_at.is_(None))
                     .order_by(Calendar.name.asc())
                 )
             ).scalars().all()