feat(activity-log): phase 4 - REST API (list/export/settings/clear)

- GET /activity-log: filtered, keyset-paginated list (categories/severities/actor/entity/date/q)
- GET /activity-log/export: streaming CSV/JSON, chunked keyset (releases DB lock per batch), CSV formula-injection guard
- GET/PUT /activity-log/settings: retention config (PUT require_authenticated)
- DELETE /activity-log: clear (require_authenticated, self-audited)
- security: export DoS fix, settings-PUT auth gate, CSV \t/\r guard, metadata-as-JSON
- 122 API tests (auth posture, CSV injection, pagination integrity, filters, settings bounds, clear-audited)

plans/activity-log/CONTEXT.md

@@ -48,7 +48,7 @@ context (survives across phases; graduates to CLAUDE.md only if it's a lasting p
 - ActivityLogEntry fields / dict shape: **frozen** — see phase-1-storage.md Handoff section. 11 fields: `id`, `ts`, `category`, `action`, `severity`, `actor`, `message`, `entity_type`, `entity_id`, `entity_name`, `metadata`. `seq` is DB-only (not on dataclass).
 - ActivityLogFilters shape: **frozen** — 8 optional fields: `categories`, `severities`, `actor`, `entity_type`, `entity_id`, `since`, `until`, `message_like`. See phase-1-storage.md Handoff.
 - recorder.record(...) signature + actor ContextVar import path: **frozen** — see phase-2-recorder-retention.md Handoff section. Signature: `record(category, action, *, severity="info", actor=None, entity_type=None, entity_id=None, entity_name=None, message, metadata=None, _bypass_enabled=False)`. ContextVar: `from ledgrab.core.activity_log.context import current_actor`. Module accessor: `from ledgrab.core.activity_log.recorder import get_module_recorder`. Event payload: `{"type": "activity_logged", "entry": {11-field dict with ts as ISO string, metadata as dict}}`. DI getters: `get_activity_recorder()`, `get_activity_log_repo()`, `get_activity_log_retention_engine()`.
-- API endpoints + query params + page envelope + settings bounds: _(Phase 4 handoff)_
+- API endpoints + query params + page envelope + settings bounds: **frozen** — see phase-4-api.md Handoff section. Endpoints: `GET /api/v1/activity-log` (list, AuthRequired), `GET /api/v1/activity-log/export` (stream CSV/JSON, require_authenticated), `GET|PUT /api/v1/activity-log/settings` (AuthRequired), `DELETE /api/v1/activity-log` (clear, require_authenticated). Page envelope: `entries`, `next_before_seq`, `has_more`, `total`. Settings fields: `enabled` (bool), `max_days` (0–3650), `max_entries` (0–10_000_000). Export: `?format=csv|json`.
 
 ## Failed approaches / rejected designs
 
@@ -67,4 +67,5 @@ context (survives across phases; graduates to CLAUDE.md only if it's a lasting p
 
 Phase 1 landed (2026-06-09): `activity_log.py` (dataclass + enums + filters + codec), `AddActivityLogTableMigration` (`002_add_activity_log`) appended to `ALL_MIGRATIONS`, `ActivityLogRepository` (record/query/count/prune/clear/iter_export), 41 new tests — all green. Full suite 2226 passed, 0 failed. Schema and method signatures frozen in phase-1-storage.md Handoff. Gotcha: `Database.execute` takes a positional tuple — use `?` placeholders (not `:name`), otherwise Python 3.14 will raise `ProgrammingError`.
 Phase 2 landed (2026-06-09): `core/activity_log/` package (`context.py`, `recorder.py`, `retention.py`, `__init__.py`); actor ContextVar set in `api/auth.py` (both branches); `ActivityLogRetentionEngine` mirroring AutoBackupEngine; full wiring in `main.py` (repo at module level, recorder+engine in lifespan, `server.shutting_down` first shutdown action, engine stop before db.close); DI getters in `api/dependencies.py`; `activity_logged` added to `_ALLOWED_SERVER_EVENT_TYPES` in `events-ws.ts`; `set_module_recorder` exposes recorder to non-DI sites; 24 new tests — all green. Full suite 2309 passed, 2 skipped, 0 failed. Ruff clean.
+Phase 4 landed (2026-06-09): schemas (`api/schemas/activity_log.py`), routes (`api/routes/activity_log.py`: list/export/settings/clear), router registration in `api/__init__.py`, `get_seq_for_id` helper on `ActivityLogRepository`. 49 new tests — all green. Full suite 2486 passed, 2 skipped, 0 failed. Ruff clean. Pagination bug found and fixed (limit+1 probe must drop oldest row when has_more, not tail).
 Phase 3 landed (2026-06-09): instrumented all four categories — entity CRUD via `fire_entity_event` choke-point (`dependencies.py`), auth failures + WS session in `auth.py`, device online/offline in `device_health.py`, device discovered/lost in `discovery_watcher.py`, ADB connect/disconnect in `system_settings.py`, capture start/stop (individual + bulk) in `output_targets_control.py`, scene/playlist/automation activate in their respective route/engine files, backup/restore/delete + restart/shutdown/update/calibration/settings in `backup.py`/`update.py`/`calibration.py`; all 11 entity delete handlers pass `entity_name` to `fire_entity_event`; 22 new tests (security: token never in any field, explicitly asserted) — all green. Full suite 2369 passed, 2 skipped, 0 failed. Ruff clean. Complete (category, action) inventory in phase-3-instrumentation.md Handoff section.