feat(activity-log): phase 5 - Activity tab (smart filtering, live updates, export)

- new top-level Activity tab: filter toolbar (category/severity chips, presets, debounced search, actor/entity/date), keyset load-more, expandable detail
- live prepend via server:activity_logged; authed CSV/JSON blob export
- formatTimestamp/formatRelativeTime in core/ui.ts; history+severity SVG icons; Ctrl+7 shortcut
- i18n activity_log.* across en/ru/zh; getting-started tutorial step; activity-log.css (themed)
- review fixes: newest-first ordering, attribute-context XSS hardening (_escapeAttr + event delegation)

plans/activity-log/CONTEXT.md

@@ -69,3 +69,4 @@ Phase 1 landed (2026-06-09): `activity_log.py` (dataclass + enums + filters + co
 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.
+Phase 5 landed (2026-06-09): Activity tab frontend — `features/activity-log.ts` (loadActivityLog, filter toolbar with category/severity chips + presets + debounced search + date range + actor/entity-type text fields, keyset-paginated list, expandable detail drawer, live-prepend via `server:activity_logged`, authed CSV/JSON blob export); `core/ui.ts` additions (`formatTimestamp`, `formatRelativeTime`); `core/icon-paths.ts` + `core/icons.ts` additions (scrollText/audit, circleAlert, info, filter, xCircle); `core/tab-registry.ts` registered; `templates/index.html` tab button + panel; `app.ts` + `global.d.ts` wired; `static/css/activity-log.css` (precision-ledger design, category color rail, live-dot pulse, detail drawer, responsive breakpoints); all three locales updated (activity_log.* + time.* relative-time keys + tour.activity_log); `features/tutorials.ts` getting-started tour extended. `tsc --noEmit` clean, `npm run build` passes. Reusable helpers for Phase 6 documented in phase-5-frontend-tab.md Handoff section.