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/auth/routes.py

@@ -21,17 +21,17 @@ from ..blog.ghost.ghost_sync import (
     sync_member_to_ghost,
 )
 
-from db.session import get_session
-from models import User, MagicLink, UserNewsletter
-from models.ghost_membership_entities import GhostNewsletter
-from config import config
-from utils import host_url
-from shared.urls import coop_url
+from shared.db.session import get_session
+from shared.models import User, MagicLink, UserNewsletter
+from shared.models.ghost_membership_entities import GhostNewsletter
+from shared.config import config
+from shared.utils import host_url
+from shared.infrastructure.urls import coop_url
 
 from sqlalchemy.orm import selectinload
-from suma_browser.app.redis_cacher import clear_cache
-from shared.cart_identity import current_cart_identity
-from shared.internal_api import post as api_post
+from shared.browser.app.redis_cacher import clear_cache
+from shared.infrastructure.cart_identity import current_cart_identity
+from shared.infrastructure.internal_api import post as api_post
 from .services import pop_login_redirect_target, store_login_redirect_target
 from .services.auth_operations import (
     get_app_host,
@@ -84,7 +84,7 @@ def register(url_prefix="/auth"):
 
     @auth_bp.get("/account/")
     async def account():
-        from suma_browser.app.utils.htmx import is_htmx_request
+        from shared.browser.app.utils.htmx import is_htmx_request
 
         if not g.get("user"):
             return redirect(host_url(url_for("auth.login_form")))
@@ -104,7 +104,7 @@ def register(url_prefix="/auth"):
 
     @auth_bp.get("/newsletters/")
     async def newsletters():
-        from suma_browser.app.utils.htmx import is_htmx_request
+        from shared.browser.app.utils.htmx import is_htmx_request
 
         if not g.get("user"):
             return redirect(host_url(url_for("auth.login_form")))

bp/auth/services/auth_operations.py

@@ -10,8 +10,8 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
 
-from models import User, MagicLink, UserNewsletter
-from config import config
+from shared.models import User, MagicLink, UserNewsletter
+from shared.config import config
 
 
 def get_app_host() -> str:

bp/auth/services/login_redirect.py

@@ -1,7 +1,7 @@
 from urllib.parse import urlparse
 from quart import session
 
-from shared.urls import coop_url
+from shared.infrastructure.urls import coop_url
 
 
 LOGIN_REDIRECT_SESSION_KEY = "login_redirect_to"