feat: Actions system — scheduled mutations on external services

Full-stack implementation of provider-scoped Actions with extensible
executor architecture. First action type: Immich auto_organize (sort
assets into albums by person, CLIP search, date range, favorites).

Core:
- ActionTypeDefinition registry + ActionExecutor ABC with execute/validate/dry-run
- ImmichActionExecutor with multi-album support and client-side filtering
- ImmichClient write methods: add/remove assets, create album, paginated search

Server:
- Action, ActionRule, ActionExecution DB models
- Full CRUD API + manual execute + dry-run + execution history endpoints
- APScheduler integration (interval + cron) for automated execution
- Action type discovery API + provider people endpoint

Frontend:
- Actions page with CRUD, execute/dry-run buttons, inline rule editor
- RuleEditor: person/album MultiEntitySelect pickers, criteria config
- ExecutionHistory: expandable per-rule result details
- MultiEntitySelect reusable component (searchable multi-pick palette)
- Notification tracker album picker migrated to MultiEntitySelect
- Fixed MdiIcon race condition (icons missing after cache-clearing reload)

frontend/src/lib/i18n/en.json

@@ -33,7 +33,9 @@
 		"targetDiscord": "Discord",
 		"targetSlack": "Slack",
 		"targetNtfy": "ntfy",
-		"targetMatrix": "Matrix"
+		"targetMatrix": "Matrix",
+		"automation": "Automation",
+		"actions": "Actions"
 	},
 	"auth": {
 		"signIn": "Sign in",
@@ -138,6 +140,7 @@
 		"server": "Provider",
 		"selectServer": "Select provider...",
 		"albums": "Albums",
+		"selectAlbums": "Select albums...",
 		"eventTypes": "Event Types",
 		"notificationTargets": "Notification Targets",
 		"scanInterval": "Scan Interval (seconds)",
@@ -828,5 +831,59 @@
 		"navigate": "navigate",
 		"open": "open",
 		"close": "close"
+	},
+	"actions": {
+		"title": "Actions",
+		"description": "Scheduled mutations on external services",
+		"addAction": "Add Action",
+		"noActions": "No actions configured yet.",
+		"provider": "Provider",
+		"selectProvider": "Select provider...",
+		"actionType": "Action Type",
+		"name": "Name",
+		"schedule": "Schedule",
+		"interval": "Interval",
+		"seconds": "seconds",
+		"cronHint": "Standard cron expression (e.g. 0 3 * * * for daily at 3 AM)",
+		"enabled": "Enabled",
+		"rules": "rules",
+		"addRule": "Add Rule",
+		"ruleName": "Rule Name",
+		"ruleNamePlaceholder": "e.g. Alice → Family Album",
+		"unnamedRule": "Unnamed rule",
+		"noRules": "No rules yet. Add a rule to define what this action does.",
+		"on": "ON",
+		"off": "OFF",
+		"criteria": "Criteria",
+		"persons": "Persons",
+		"addPerson": "Add person...",
+		"searchQuery": "Smart Search Query",
+		"searchQueryPlaceholder": "e.g. sunset, beach, birthday...",
+		"assetType": "Asset type",
+		"dateFrom": "From date",
+		"dateTo": "To date",
+		"favoritesOnly": "Favorites only",
+		"targetAlbum": "Target Album",
+		"selectAlbum": "Album",
+		"selectAlbumPlaceholder": "— Select album —",
+		"albumId": "Album ID",
+		"createAlbumIfMissing": "Create album if it doesn't exist",
+		"newAlbumName": "New album name",
+		"execute": "Execute",
+		"dryRun": "Dry Run",
+		"history": "History",
+		"affected": "affected",
+		"executeResult": "Action executed: {affected} items affected",
+		"dryRunResult": "Dry run: {affected} items would be affected",
+		"saved": "Action saved",
+		"deleted": "Action deleted",
+		"ruleSaved": "Rule saved",
+		"ruleDeleted": "Rule deleted",
+		"confirmDelete": "Are you sure you want to delete this action? All rules and execution history will be lost.",
+		"loadError": "Failed to load actions",
+		"noExecutions": "No executions yet.",
+		"triggerManual": "manual",
+		"triggerDryRun": "dry-run",
+		"triggerScheduled": "scheduled"
 	}
 }