Fix JWT signature verification by requesting correct token audience

- Change frontend apiTokenRequest scopes from OpenID-only to CLIENT_ID/.default
  This makes Azure AD issue tokens with audience = app client ID instead of Graph API
- Add diagnostic logging in backend to show token claims before verification
- Fixes 401 Unauthorized errors on all API calls after login

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/auth_service.py

@@ -82,6 +82,15 @@ async def verify_access_token(token: str) -> Optional[dict]:
         alg = unverified_header.get("alg")
         logger.info(f"[MSAL Backend] Token header - kid: {kid}, alg: {alg}")
 
+        # Log unverified claims to see what we're receiving
+        try:
+            unverified_claims = jwt.get_unverified_claims(token)
+            logger.info(f"[MSAL Backend] Token aud (unverified): {unverified_claims.get('aud')}")
+            logger.info(f"[MSAL Backend] Token iss (unverified): {unverified_claims.get('iss')}")
+            logger.info(f"[MSAL Backend] Token azp (unverified): {unverified_claims.get('azp')}")
+        except Exception as e:
+            logger.warning(f"[MSAL Backend] Could not decode unverified claims: {e}")
+
         if not kid:
             logger.warning("[MSAL Backend] No key ID in token header")
             return None

frontend/services/authConfig.ts

@@ -4,10 +4,13 @@
  */
 import { Configuration, LogLevel, PopupRequest } from '@azure/msal-browser';
 
+// Client ID used for both MSAL config and API token requests
+const CLIENT_ID = import.meta.env.VITE_AZURE_CLIENT_ID || '';
+
 // MSAL configuration - uses PKCE by default for SPAs
 export const msalConfig: Configuration = {
     auth: {
-        clientId: import.meta.env.VITE_AZURE_CLIENT_ID || '',
+        clientId: CLIENT_ID,
         authority: `https://login.microsoftonline.com/${import.meta.env.VITE_AZURE_TENANT_ID || 'common'}`,
         redirectUri: import.meta.env.VITE_AZURE_REDIRECT_URI || window.location.origin,
         postLogoutRedirectUri: window.location.origin,
@@ -41,13 +44,13 @@ export const msalConfig: Configuration = {
     },
 };
 
-// Scopes for the access token
-// Using basic OpenID scopes for authentication
+// Scopes for initial login (ID token)
 export const loginRequest: PopupRequest = {
     scopes: ['openid', 'profile', 'email'],
 };
 
-// Scopes for API calls (same as login for this app)
+// Scopes for API calls - request token for OUR app, not Graph
+// Using the client ID as scope requests an access token for this app
 export const apiTokenRequest = {
-    scopes: ['openid', 'profile', 'email'],
+    scopes: [`${CLIENT_ID}/.default`],
 };