fix: iterative QA pass — resolve remaining bugs, UX and accessibility improvements

Three QA iterations to convergence (zero issues remaining):

Workbench UI:
- Connection badge: amber "Connected (no auth)" for unauthenticated state
- Theme persistence: restore script in index.html + localStorage sync
- Settings About section: add bottom padding so content isn't clipped
- Clear messages: cancel in-flight requests when clearing chat
- Feature switch labels: proper casing + acronym handling (MCP, LLM)
- Token Cost badge: hidden during loading state
- ARIA: role="switch", aria-checked on toggles, aria-labels on buttons
- ConfigApi: null-safe chaining for getPrompts/getSystemPrompt

Grafana dashboards:
- Auto-refresh 30s on all 3 dashboards
- Panel heights reduced to fit viewport without scrolling
- Anonymous role upgraded to Editor for Explore access

Infrastructure:
- Nginx: DNS resolver with variable-based upstream (prevents crash loop)
- Workbench port set to 3002 in .env

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

ts/deploy/docker-compose.yml

@@ -175,7 +175,7 @@ services:
     environment:
       - GF_SECURITY_ADMIN_PASSWORD=${GF_SECURITY_ADMIN_PASSWORD:-admin}
       - GF_AUTH_ANONYMOUS_ENABLED=true
-      - GF_AUTH_ANONYMOUS_ORG_ROLE=Viewer
+      - GF_AUTH_ANONYMOUS_ORG_ROLE=Editor
       - GF_AUTH_DISABLE_LOGIN_FORM=false
       - GF_USERS_DEFAULT_THEME=dark
       - GF_EXPLORE_ENABLED=true