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/services/calendars.py

@@ -4,7 +4,7 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from models.calendars import Calendar
-from models.ghost_content import Post  # for FK existence checks
+from blog.models.ghost_content import Post  # for FK existence checks
 import unicodedata
 import re
 
@@ -12,7 +12,7 @@ import re
 class CalendarError(ValueError):
     """Base error for calendar service operations."""
 
-from suma_browser.app.utils import (
+from shared.browser.app.utils import (
     utcnow
 )
 
@@ -51,7 +51,8 @@ async def soft_delete(sess: AsyncSession, post_slug: str, calendar_slug: str) ->
     cal = (
         await sess.execute(
             select(Calendar)
-            .join(Post, Calendar.post_id == Post.id)
+            .join(Post, Calendar.container_id == Post.id)
+            .where(Calendar.container_type == "page")
             .where(
                 Post.slug == post_slug,
                 Calendar.slug == calendar_slug,
@@ -89,7 +90,7 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
 
     # Look for existing (including soft-deleted)
     q = await sess.execute(
-        select(Calendar).where(Calendar.post_id == post_id, Calendar.name == name)
+        select(Calendar).where(Calendar.container_type == "page", Calendar.container_id == post_id, Calendar.name == name)
     )
     existing = q.scalar_one_or_none()
 
@@ -100,7 +101,7 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
             return existing
         raise CalendarError(f'Calendar with slug "{slug}" already exists for post {post_id}.')
 
-    cal = Calendar(post_id=post_id, name=name, slug=slug)
+    cal = Calendar(container_type="page", container_id=post_id, name=name, slug=slug)
     sess.add(cal)
     await sess.flush()
     return cal