sync-event toasts, image pull ordering, stale banner field diff

- replace chat-bot sync notifications with a dedicated relay_sync_events
  queue: POST/GET /api/sync-events, drained by /api/relay/poll and
  surfaced as stacking toasts via caldav.js. Old /api/chat/bot removed,
  bot=1 rows purged on bootstrap, orange bot rendering dropped from
  relay UI. Chat thread stays clean.
- collab pull: fetch attachments BEFORE applying the body so the moment
  state.cards reflects the new reference the file is on disk. Fixes the
  "preview shows broken/missing image, editor shows it" race where the
  browser cached the 404 between attachment landing and user re-render.
- detail stale banner now compares title/body/color/tags in addition to
  updated_at — robust against second-granularity timestamp collisions
  and any other case where updated_at doesn't tick but content differs.

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

config.php

@@ -1,7 +1,7 @@
 <?php
 
 define('APP_NAME', 'hyprcrd');
-define('APP_VERSION', '1.7.0');
+define('APP_VERSION', '1.8.0');
 
 // Database path — writable directory, outside webroot
 // DB_PATH / UPLOAD_DIR can be pre-defined by the Electron router for app isolation