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

Phase 1-3 of decoupling:
- path_setup.py adds project root to sys.path
- Blog-owned models in blog/models/ (ghost_content, snippet, tag_group)
- Re-export shims for shared models (user, kv, magic_link, menu_item)
- All imports updated: shared.infrastructure, shared.db, shared.browser, etc.
- No more cross-app post_id FKs in calendar/market/page_config

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

bp/post/services/entry_associations.py

@@ -4,7 +4,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select
 from sqlalchemy.sql import func
 
-from models.calendars import CalendarEntry, CalendarEntryPost, Calendar
+from events.models.calendars import CalendarEntry, CalendarEntryPost, Calendar
 from models.ghost_content import Post
 
 
@@ -35,7 +35,8 @@ async def toggle_entry_association(
     existing = await session.scalar(
         select(CalendarEntryPost).where(
             CalendarEntryPost.entry_id == entry_id,
-            CalendarEntryPost.post_id == post_id,
+            CalendarEntryPost.content_type == "post",
+            CalendarEntryPost.content_id == post_id,
             CalendarEntryPost.deleted_at.is_(None)
         )
     )
@@ -49,7 +50,8 @@ async def toggle_entry_association(
         # Create association
         association = CalendarEntryPost(
             entry_id=entry_id,
-            post_id=post_id
+            content_type="post",
+            content_id=post_id
         )
         session.add(association)
         await session.flush()
@@ -67,7 +69,8 @@ async def get_post_entry_ids(
     result = await session.execute(
         select(CalendarEntryPost.entry_id)
         .where(
-            CalendarEntryPost.post_id == post_id,
+            CalendarEntryPost.content_type == "post",
+            CalendarEntryPost.content_id == post_id,
             CalendarEntryPost.deleted_at.is_(None)
         )
     )
@@ -88,7 +91,8 @@ async def get_associated_entries(
     entry_ids_result = await session.execute(
         select(CalendarEntryPost.entry_id)
         .where(
-            CalendarEntryPost.post_id == post_id,
+            CalendarEntryPost.content_type == "post",
+            CalendarEntryPost.content_id == post_id,
             CalendarEntryPost.deleted_at.is_(None)
         )
     )