Refactor HAOS integration to use shared core library (Phase 2)

Wire the integration to delegate all HA-independent logic to
immich-watcher-core, eliminating ~2300 lines of duplicated code.

Changes:
- const.py: Import shared constants from core, keep HA-specific ones
- storage.py: Create HAStorageBackend adapter wrapping HA's Store,
  use core TelegramFileCache and NotificationQueue via adapter
- coordinator.py: Delegate to core ImmichClient for API calls,
  detect_album_changes() for change detection, and asset_utils
  for filtering/sorting/URL building. Keep HA-specific event firing.
- sensor.py: Replace ~1300 lines of Telegram code with 15-line
  delegation to core TelegramClient. Keep entity classes unchanged.
- __init__.py: Use factory functions for creating core instances
  with HA storage backends
- manifest.json: Add immich-watcher-core dependency

Integration line count: 3600 -> 1295 lines (-64%)
Zero behavior changes for end users.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plans/phase-2-haos-refactor.md

@@ -0,0 +1,75 @@
+# Phase 2: Wire Core Library into HAOS Integration
+
+**Status**: In progress
+**Parent**: [primary-plan.md](primary-plan.md)
+
+---
+
+## Goal
+
+Refactor the HAOS integration to delegate to `immich-watcher-core` for all HA-independent logic, reducing duplication and preparing for the standalone server.
+
+---
+
+## Important: HACS Compatibility
+
+HACS requires `custom_components/<domain>/` at the repository root. We **cannot** move it to `packages/haos/`. Instead:
+
+- `custom_components/` stays at repo root
+- The integration imports from `immich_watcher_core` (the core library)
+- `manifest.json` lists `immich-watcher-core` in `requirements` (for future PyPI publish)
+- During development, `pip install -e packages/core` makes imports work
+- For HACS distribution, we'll publish the core to PyPI
+
+---
+
+## Tasks
+
+### 1. Update manifest.json `[ ]`
+- Add `immich-watcher-core` to requirements list
+- Do NOT bump version (only plans/core changed, not integration content yet)
+
+### 2. Refactor const.py `[ ]`
+- Import shared constants from `immich_watcher_core.constants`
+- Keep HA-specific constants (DOMAIN, CONF_*, PLATFORMS, SERVICE_*) local
+- Re-export shared constants for backward compatibility with other integration files
+
+### 3. Refactor storage.py `[ ]`
+- Create `HAStorageBackend` adapter wrapping `homeassistant.helpers.storage.Store`
+  that satisfies `StorageBackend` protocol from core
+- Replace `TelegramFileCache` with core's version using `HAStorageBackend`
+- Replace `NotificationQueue` with core's version using `HAStorageBackend`
+- Keep `ImmichAlbumStorage` as-is (HA-specific album state management)
+
+### 4. Refactor coordinator.py `[ ]`
+- Remove dataclass definitions (SharedLinkInfo, AssetInfo, AlbumData, AlbumChange) — import from core
+- Replace Immich API methods with `ImmichClient` from core
+- Replace `_detect_change()` with `detect_album_changes()` from core
+- Replace `_build_asset_detail()` and URL helpers with `asset_utils` from core
+- Replace `async_get_assets()` filtering/sorting with `filter_assets()` + `sort_assets()` from core
+- Keep HA-specific: `DataUpdateCoordinator` subclass, `_fire_events()`, `async_get_clientsession()`
+
+### 5. Refactor sensor.py `[ ]`
+- Remove Telegram constants, helper functions, and all `_send_telegram_*` methods
+- Replace with `TelegramClient` from core in `_execute_telegram_notification()`
+- Keep HA-specific: entity classes, service registration, platform setup
+
+### 6. Update __init__.py `[ ]`
+- Update imports for new storage classes (HAStorageBackend adapter)
+- Create TelegramFileCache instances using core class + HA adapter
+
+### 7. Verify `[ ]`
+- All existing entities, services, and events work identically
+- Telegram notifications work with caching
+- Quiet hours queueing works
+- No HA import in core library (verify with grep)
+
+---
+
+## Acceptance Criteria
+
+- [ ] Integration imports and delegates to `immich_watcher_core`
+- [ ] Zero behavior changes for end users
+- [ ] No duplicated logic between core and integration
+- [ ] Core library has no HA imports (verified)
+- [ ] `ImmichAlbumStorage` is the only storage class still HA-native