feat: Home Assistant provider — WebSocket subscription + bot commands

Adds Home Assistant as a service provider with two coordinated surfaces:

Notifications (subscription):
- Long-lived WebSocket client (aiohttp ws_connect) with auth handshake,
  exponential-backoff reconnect, bounded event queue, and area-registry
  enrichment cached per (re)connect
- ServiceProvider ABC gains an optional `subscribe()` method for push-style
  providers; HomeAssistantServiceProvider uses it via a per-provider
  supervisor task started in the FastAPI lifespan
- 4 event types (state_changed, automation_triggered, call_service,
  event_fired), 4 default Jinja templates (en + ru), HA-specific
  tracker filters (entity_glob, domain_allowlist, exact entity ids)
- Extracted shared dispatch pipeline (api/webhooks.py → services/
  event_dispatch.py) so subscription and webhook ingest share the same
  event_log + deferred-dispatch + quiet-hours code path

Bot commands:
- /status, /entities [glob], /state <entity_id>, /areas
- Multi-command WS session so /status and /areas cost one handshake
- Sensitive-attribute blocklist (camera access_token, entity_picture, etc.)
  and 30-attribute cap to keep /state output safe and within Telegram's
  message size
- Error-message redaction strips URL userinfo before surfacing to chat

Frontend:
- HA descriptor with toggle ConfigField type (new) and tag-input filter
  mode for free-text glob/domain lists (new TagInput component)
- 15 command slots + 4 notification slots wired into the existing
  template-config UI

frontend/src/routes/providers/+page.svelte

@@ -321,6 +321,11 @@
 					<input id="prv-{field.key}" type="number" bind:value={form[field.key]}
 						min={field.min} max={field.max}
 						class="w-full px-3 py-2 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]" />
+				{:else if field.type === 'toggle'}
+					<label class="toggle-switch">
+						<input id="prv-{field.key}" type="checkbox" bind:checked={form[field.key]} />
+						<span class="toggle-track"></span>
+					</label>
 				{:else}
 					<input id="prv-{field.key}" type={field.type} bind:value={form[field.key]}
 						required={field.required === true || (field.required === 'create-only' && !editing)}