feat(modules): group-docs schema + kind-generalized registry (§11.6 docs C1)

Data layer for extending shared group collections from KV to docs. KV behavior
unchanged (callers pass kind="kv").

- 0054_group_docs.sql: widen the group_collections kind CHECK to ('kv','docs')
  and add the group-keyed group_docs store (clone of docs/0013, keyed by
  group_id, CASCADE on group delete) + its (group_id,collection) and data GIN
  indexes.
- group_collection_repo: thread a `kind` parameter through list_for_owner,
  resolve_owning_group, insert/delete_collection_tx; add list_all_for_owner ->
  (name,kind) for the kind-aware diff (D4). Relocate the injectable
  GroupCollectionResolver trait + Postgres impl here (now shared by kv+docs;
  resolve takes kind) — was in group_kv_service.
- group_docs_repo: a near-clone of docs_repo keyed by group_id; find reuses the
  generalized build_find_query.
- docs_repo: generalize build_find_query(table, owner_col, owner_id, …) — both
  are compile-time literals (no injection); app docs passes ("docs","app_id"),
  group docs ("group_docs","group_id"). row_to_doc/build_find_query are now
  pub(crate) for reuse.

Schema snapshot re-blessed (55 migrations).

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

crates/manager-core/src/lib.rs

@@ -51,6 +51,7 @@ pub mod files_service;
 pub mod files_sweep;
 pub mod gc;
 pub mod group_collection_repo;
+pub mod group_docs_repo;
 pub mod group_kv_repo;
 pub mod group_kv_service;
 pub mod group_members_repo;
@@ -179,10 +180,10 @@ pub use files_repo::{FilesConfig, FilesRepo, FilesRepoError, FsFilesRepo};
 pub use files_service::FilesServiceImpl;
 pub use files_sweep::{spawn_files_orphan_sweep, sweep_orphan_tmp_files, SweepStats};
 pub use gc::{spawn_abandoned_gc, spawn_app_user_token_gc, spawn_dead_letter_gc};
+pub use group_collection_repo::{GroupCollectionResolver, PostgresGroupCollectionResolver};
+pub use group_docs_repo::{GroupDocsRepo, GroupDocsRepoError, PostgresGroupDocsRepo};
 pub use group_kv_repo::{GroupKvRepo, GroupKvRepoError, PostgresGroupKvRepo};
-pub use group_kv_service::{
-    GroupCollectionResolver, GroupKvServiceImpl, PostgresGroupCollectionResolver,
-};
+pub use group_kv_service::GroupKvServiceImpl;
 pub use group_members_repo::{
     GroupMembersRepository, GroupMembersRepositoryError, GroupMembershipDetail, GroupMembershipRow,
     PostgresGroupMembersRepository,