refactor(data): introduce simple query helper

docs/development/simple-query-inventory.md

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+# Aether Data Simple Query Inventory
+
+This inventory tracks repository read paths that are intended to use the
+internal `aether-data-query` helpers. The helper layer is for SQL fragments only:
+repositories still own their table-specific projections, joins, row mapping, and
+business rules.
+
+## Included In This Pass
+
+- `background_tasks`
+  - `find_run`
+  - `list_runs`
+  - `list_events`
+  - simple `summarize_runs` count/group reads remain behavior-locked in SQL
+- `announcements`
+  - `find_by_id`
+  - `list_announcements`
+  - `count_unread_active_announcements`
+- `auth_modules`
+  - `list_enabled_oauth_providers`
+  - `get_ldap_config`
+- `oauth_providers`
+  - `list_oauth_provider_configs`
+  - `get_oauth_provider_config`
+- `quota`
+  - `find_by_provider_id`
+  - `find_by_provider_ids`
+- `provider_catalog`
+  - provider by-id/provider list reads in PG/SQLite
+  - endpoint/key by-id and by-provider-id `IN` reads in PG/SQLite
+  - provider key page filters, search, order, limit/offset in PG/SQLite
+  - key stats by provider ids in PG/SQLite
+- `proxy_nodes`
+  - node list/find reads
+  - event list/filter reads
+- `management_tokens`
+  - `list_management_tokens`
+  - `get_management_token_with_user`
+  - `get_management_token_with_user_by_hash`
+- `pool_scores`
+  - `find_scores_by_identity`
+  - `list_ranked_pool_members`
+  - `list_pool_member_scores`
+  - `list_pool_member_probe_candidates`
+  - `get_pool_member_scores_by_ids`
+- `candidates`
+  - `list_by_request_id`
+  - `list_recent`
+  - `list_by_provider_id`
+  - `list_finalized_by_endpoint_ids_since`
+  - simple finalized status count
+- `gemini_file_mappings`
+  - list/count filters and search
+
+## Deferred
+
+- `usage` aggregation, dashboard, leaderboard, cache-hit, provider/key/user
+  statistics, rebuild paths, and body/blob reads.
+- `candidate_selection` JSON/alias matching and scoring.
+- `wallet` ledger, order, refund, callback, and redeem-code list logic.
+- write/upsert/delete paths, transactions, `RETURNING`, CTEs, window functions,
+  advisory locks, and schema compatibility probes.
+- MySQL `provider_catalog` still delegates read paths through the existing
+  memory adapter; migrate it in a focused follow-up so MySQL parity can be tested
+  independently.
+- `users/auth` and `global_models` still contain additional simple read paths.
+  `global_models/sqlite.rs` had pre-existing local edits and must be handled
+  carefully in a dedicated slice.
+
+## Helper Coverage
+
+- dialect-aware identifier quoting
+- `WHERE`/`AND` sequencing
+- equality and optional equality filters
+- `IN` filters
+- case-insensitive contains/search
+- whitelisted order-by rendering
+- `LIMIT` and `LIMIT/OFFSET`