Fix login persistence with AUTH_SEND_JWT_HEADER enabled

With AUTH_SEND_JWT_HEADER=true, frontend now properly handles JWT authentication:
- Store JWT token in client-side cookie named 'JWT'
- Extract and store XSRF token from JWT payload
- Set Secure flag automatically when on HTTPS connection
- Update documentation to clarify this behavior

This fixes an issue where login state would be lost after page reload
when using header-based JWT authentication.

frontend/pnpm-lock.yaml

@@ -4994,7 +4994,7 @@ packages:
       normalize-path: 3.0.0
       readdirp: 3.6.0
     optionalDependencies:
-      fsevents: 2.3.2
+      fsevents: 2.3.3
     dev: true
 
   /chrome-trace-event@1.0.3:
@@ -6986,14 +6986,6 @@ packages:
     resolution: {integrity: sha512-OO0pH2lK6a0hZnAdau5ItzHPI6pUlvI7jMVnxUQRtw4owF2wk8lOSabtGDCTP4Ggrg2MbGnWO9X8K1t4+fGMDw==}
     dev: true
 
-  /fsevents@2.3.2:
-    resolution: {integrity: sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==}
-    engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
-    os: [darwin]
-    requiresBuild: true
-    dev: true
-    optional: true
-
   /fsevents@2.3.3:
     resolution: {integrity: sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==}
     engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
@@ -8225,7 +8217,7 @@ packages:
       micromatch: 4.0.5
       walker: 1.0.8
     optionalDependencies:
-      fsevents: 2.3.2
+      fsevents: 2.3.3
     dev: true
 
   /jest-haste-map@28.1.3:
@@ -8244,7 +8236,7 @@ packages:
       micromatch: 4.0.5
       walker: 1.0.8
     optionalDependencies:
-      fsevents: 2.3.2
+      fsevents: 2.3.3
     dev: true
 
   /jest-leak-detector@28.1.3: