fix: diagnostic toggle hint, link_stats schema, pagination UX, rate-limit feedback

- inspector.html: collapsible section hint text now toggles between [expand]/[collapse] when clicked
- inspector.html: timeout and connection-loss during diagnostic poll now show a Retry button instead of a dead end
- inspector.html: 429 rate-limit response shows a clear human-readable message instead of generic error
- app.py: empty link_stats fallback now includes unifi_switches:{} for schema consistency with real data shape
- index.html: pagination overflow notice now says "export all as JSON" (opens in new tab) instead of misleadingly linking to raw API as navigation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/index.html

@@ -92,7 +92,7 @@
     <div id="events-table-wrap">
     {% if events %}
     {% if total_active is defined and total_active > events|length %}
-    <div class="pagination-notice">Showing {{ events|length }} of {{ total_active }} active alerts &mdash; <a href="/api/events?limit=1000">view all via API</a></div>
+    <div class="pagination-notice">Showing {{ events|length }} of {{ total_active }} active alerts — use the search box to filter, or <a href="/api/events?limit=1000" target="_blank" rel="noopener">export all as JSON</a></div>
     {% endif %}
     <div class="lt-table-wrap">
       <table class="lt-table" id="events-table">