Decouple per-service Alembic migrations and fix cross-DB queries

Each service (blog, market, cart, events, federation, account) now owns
its own database schema with independent Alembic migrations. Removes the
monolithic shared/alembic/ that ran all migrations against a single DB.

- Add per-service alembic.ini, env.py, and 0001_initial.py migrations
- Add shared/db/alembic_env.py helper with table-name filtering
- Fix cross-DB FK in blog/models/snippet.py (users lives in db_account)
- Fix cart_impl.py cross-DB queries: fetch products and market_places
  via internal data endpoints instead of direct SQL joins
- Fix blog ghost_sync to fetch page_configs from cart via data endpoint
- Add products-by-ids and page-config-ensure data endpoints
- Update all entrypoint.sh to create own DB and run own migrations
- Cart now uses db_cart instead of db_market
- Add docker-compose.dev.yml, dev.sh for local development
- CI deploys both rose-ash swarm stack and rose-ash-dev compose stack
- Fix Quart namespace package crash (root_path in factory.py)

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

events/alembic/env.py

@@ -0,0 +1,13 @@
+from alembic import context
+from shared.db.alembic_env import run_alembic
+
+MODELS = [
+    "shared.models.calendars",
+]
+
+TABLES = frozenset({
+    "calendars", "calendar_entries", "calendar_slots",
+    "ticket_types", "tickets", "calendar_entry_posts",
+})
+
+run_alembic(context.config, MODELS, TABLES)