§22 S1: thread collection_id through backend + update tests (N=1 unchanged, 454 green)

- collections.py resolution helpers (default_collection_id, type, initial_state)
- registry mirror writes project grouping fields + default-collection corpus fields
- auth.project_of_rfc joins collections; project_member_role reads memberships
- cache/api_*/funder writers+readers re-keyed to collection_id (cached_prs + denormalised
  project_id tags unchanged); api_deployment reads type/initial_state from the default collection
- projects.py restamp detects bootstrap via collections; initial_state via collection
- tests updated to the three-tier schema; test_migration_028 retired (superseded by 029)
- add @S1 acceptance test (collection grain + N=1 serving)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/funder.py

@@ -220,7 +220,7 @@ def add_consent(user_id: int, slug: str) -> None:
     db.conn().execute(
         """
         INSERT INTO funder_consents (user_id, rfc_slug) VALUES (?, ?)
-        ON CONFLICT(project_id, user_id, rfc_slug) DO NOTHING
+        ON CONFLICT(collection_id, user_id, rfc_slug) DO NOTHING
         """,
         (user_id, slug),
     )