feat(modules): group-collection registry + group-KV storage schema (§11.6 C1)

Data layer for shared cross-app group collections (KV-only MVP), nothing wired
yet. Two migrations + two repos, modeled on the extension_points (0051) marker
and the kv_entries (0007) store:

- 0052_group_collections.sql: owner-polymorphic marker table declaring a
  collection name group-shared, with a `kind` discriminator (CHECK 'kv' for
  now; generalizes to docs/files/topics/queue later) and per-owner
  partial-unique (owner, LOWER(name), kind) indexes. CASCADE — a marker is
  config, not code.
- 0053_group_kv_entries.sql: the shared store, keyed by (group_id, collection,
  key) — NO app_id (a shared row belongs to the group). CASCADE on group delete
  (data dies with its group, like vars/secrets config; an app delete leaves it).
- group_collection_repo: list_for_owner, insert/delete_collection_tx, and the
  load-bearing resolve_owning_group — walks the reading app's chain
  (CHAIN_LEVELS_CTE) for the nearest ancestor group declaring the name
  (nearest-wins via ORDER BY depth LIMIT 1). That walk IS the isolation
  boundary; the join is on group_owner only.
- group_kv_repo: a near-clone of kv_repo keyed by group_id.

Schema snapshot re-blessed (53 migrations).

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

crates/manager-core/tests/expected_schema.txt

@@ -222,6 +222,23 @@ table: files_trigger_details
   collection_glob: text NOT NULL
   ops: ARRAY NOT NULL
 
+table: group_collections
+  id: uuid NOT NULL default=gen_random_uuid()
+  group_id: uuid NULL
+  app_id: uuid NULL
+  name: text NOT NULL
+  kind: text NOT NULL default='kv'::text
+  created_at: timestamp with time zone NOT NULL default=now()
+  updated_at: timestamp with time zone NOT NULL default=now()
+
+table: group_kv_entries
+  group_id: uuid NOT NULL
+  collection: text NOT NULL
+  key: text NOT NULL
+  value: jsonb NOT NULL
+  created_at: timestamp with time zone NOT NULL default=now()
+  updated_at: timestamp with time zone NOT NULL default=now()
+
 table: group_members
   group_id: uuid NOT NULL
   user_id: uuid NOT NULL
@@ -485,6 +502,17 @@ indexes on files:
 indexes on files_trigger_details:
   files_trigger_details_pkey: public.files_trigger_details USING btree (trigger_id)
 
+indexes on group_collections:
+  group_collections_app_id_idx: public.group_collections USING btree (app_id) WHERE (app_id IS NOT NULL)
+  group_collections_app_uidx: public.group_collections USING btree (app_id, lower(name), kind) WHERE (app_id IS NOT NULL)
+  group_collections_group_id_idx: public.group_collections USING btree (group_id) WHERE (group_id IS NOT NULL)
+  group_collections_group_uidx: public.group_collections USING btree (group_id, lower(name), kind) WHERE (group_id IS NOT NULL)
+  group_collections_pkey: public.group_collections USING btree (id)
+
+indexes on group_kv_entries:
+  group_kv_entries_pkey: public.group_kv_entries USING btree (group_id, collection, key)
+  idx_group_kv_entries_group_collection: public.group_kv_entries USING btree (group_id, collection)
+
 indexes on group_members:
   group_members_pkey: public.group_members USING btree (group_id, user_id)
   group_members_user_id_idx: public.group_members USING btree (user_id)
@@ -685,6 +713,17 @@ constraints on files_trigger_details:
   [FOREIGN KEY] files_trigger_details_trigger_id_fkey: FOREIGN KEY (trigger_id) REFERENCES triggers(id) ON DELETE CASCADE
   [PRIMARY KEY] files_trigger_details_pkey: PRIMARY KEY (trigger_id)
 
+constraints on group_collections:
+  [CHECK] group_collections_kind_check: CHECK ((kind = 'kv'::text))
+  [CHECK] group_collections_owner_exactly_one: CHECK (((group_id IS NULL) <> (app_id IS NULL)))
+  [FOREIGN KEY] group_collections_app_id_fkey: FOREIGN KEY (app_id) REFERENCES apps(id) ON DELETE CASCADE
+  [FOREIGN KEY] group_collections_group_id_fkey: FOREIGN KEY (group_id) REFERENCES groups(id) ON DELETE CASCADE
+  [PRIMARY KEY] group_collections_pkey: PRIMARY KEY (id)
+
+constraints on group_kv_entries:
+  [FOREIGN KEY] group_kv_entries_group_id_fkey: FOREIGN KEY (group_id) REFERENCES groups(id) ON DELETE CASCADE
+  [PRIMARY KEY] group_kv_entries_pkey: PRIMARY KEY (group_id, collection, key)
+
 constraints on group_members:
   [CHECK] group_members_role_check: CHECK ((role = ANY (ARRAY['app_admin'::text, 'editor'::text, 'viewer'::text])))
   [FOREIGN KEY] group_members_group_id_fkey: FOREIGN KEY (group_id) REFERENCES groups(id) ON DELETE CASCADE
@@ -822,3 +861,5 @@ constraints on vars:
   0049: group secrets
   0050: group scripts
   0051: extension points
+  0052: group collections
+  0053: group kv entries