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/packages/client/src/socket/trustgraph-socket.ts

@@ -2060,7 +2060,8 @@ export class ConfigApi {
         string,
         Record<string, Record<string, string>>
       >;
-      return JSON.parse(config.config.prompt["template-index"]);
+      const raw = config.config?.prompt?.["template-index"];
+      return raw ? JSON.parse(raw) : [];
     });
   }
 
@@ -2073,7 +2074,8 @@ export class ConfigApi {
         string,
         Record<string, Record<string, string>>
       >;
-      return JSON.parse(config.config.prompt[`template.${id}`]);
+      const raw = config.config?.prompt?.[`template.${id}`];
+      return raw ? JSON.parse(raw) : null;
     });
   }
 
@@ -2086,7 +2088,8 @@ export class ConfigApi {
         string,
         Record<string, Record<string, string>>
       >;
-      return JSON.parse(config.config.prompt.system);
+      const raw = config.config?.prompt?.system;
+      return raw ? JSON.parse(raw) : "";
     });
   }