hotfix(v1.7.9): auth diagnostics and rate-limit exemptions

- Exempt /api/config/auth, /api/config/features, /health, /metrics from rate limiting
- Fix generic exception handler to return proper JSON for HTTPException instead of re-raising
- Add startup log with auth_enabled and version
- Add frontend console logging for auth config fetch errors
- Show 'Auth: OFF' or 'Auth: misconfigured' on auth button instead of empty text
- Add backend debug logging to /api/config/auth endpoint

backend/frontend/index.html

@@ -591,9 +591,15 @@
         async initAuth() {
           try {
             const res = await fetch('/api/config/auth');
-            this.authConfig = await res.json();
-          } catch {
-            this.authConfig = { auth_enabled: false };
+            if (!res.ok) {
+              console.error('Auth config fetch failed:', res.status, res.statusText);
+              this.authConfig = { auth_enabled: false, _error: res.status };
+            } else {
+              this.authConfig = await res.json();
+            }
+          } catch (err) {
+            console.error('Auth config fetch error:', err);
+            this.authConfig = { auth_enabled: false, _error: 'network' };
           }
 
           try {
@@ -614,7 +620,17 @@
           }
 
           if (!this.authConfig?.auth_enabled) {
-            this.authBtnText = '';
+            this.authBtnText = 'Auth: OFF';
+            console.warn('AOC auth is disabled. Set AUTH_ENABLED=true in .env to enable login.');
+            return;
+          }
+
+          const tenantId = this.authConfig.tenant_id;
+          const clientId = this.authConfig.client_id;
+          if (!clientId || !tenantId) {
+            this.authBtnText = 'Auth: misconfigured';
+            this.statusText = 'Auth is enabled but client_id or tenant_id is missing. Check .env configuration.';
+            console.error('AOC auth misconfigured: missing client_id or tenant_id in /api/config/auth');
             return;
           }
 
@@ -623,8 +639,6 @@
             return;
           }
 
-          const tenantId = this.authConfig.tenant_id;
-          const clientId = this.authConfig.client_id;
           const baseScope = this.authConfig.scope || "";
           this.authScopes = Array.from(new Set(['openid', 'profile', 'email', ...baseScope.split(/[ ,]+/).filter(Boolean)]));
           const authority = `https://login.microsoftonline.com/${tenantId}`;