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/tickets/routes.py

@@ -17,8 +17,8 @@ from sqlalchemy import select
 from sqlalchemy.orm import selectinload
 
 from models.calendars import CalendarEntry
-from shared.cart_identity import current_cart_identity
-from suma_browser.app.redis_cacher import clear_cache
+from shared.infrastructure.cart_identity import current_cart_identity
+from shared.browser.app.redis_cacher import clear_cache
 
 from .services.tickets import (
     create_ticket,
@@ -37,7 +37,7 @@ def register() -> Blueprint:
     @bp.get("/")
     async def my_tickets():
         """List all tickets for the current user/session."""
-        from suma_browser.app.utils.htmx import is_htmx_request
+        from shared.browser.app.utils.htmx import is_htmx_request
 
         ident = current_cart_identity()
         tickets = await get_user_tickets(
@@ -62,7 +62,7 @@ def register() -> Blueprint:
     @bp.get("/<code>/")
     async def ticket_detail(code: str):
         """View a single ticket with QR code."""
-        from suma_browser.app.utils.htmx import is_htmx_request
+        from shared.browser.app.utils.htmx import is_htmx_request
 
         ticket = await get_ticket_by_code(g.s, code)
         if not ticket:

bp/tickets/services/tickets.py

@@ -14,6 +14,7 @@ from sqlalchemy.orm import selectinload
 from models.calendars import Ticket, TicketType, CalendarEntry
 
 
+
 async def create_ticket(
     session: AsyncSession,
     *,