Refactor permission handling and authentication services

Replaced `PermissionClaim` enum with an OpenAPI-defined schema `PermissionClaimDto` for consistency across frontend and backend. Refactored authentication flow to utilize `AuthService` on the frontend, consolidating JWT handling logic. Removed redundant methods like `saveJwt` and integrated robust permission management throughout the application.

open_api/src/main/resources/api.yml

@@ -6,6 +6,10 @@ info:
   version: 1.0.0
 servers:
   - url: https://alttd.com/api/v3
+components:
+  schemas:
+    PermissionClaim:
+      $ref: './schemas/permissions/permissions.yml#/components/schemas/PermissionClaim'
 tags:
   - name: history
     description: Retrieves punishment history

open_api/src/main/resources/schemas/permissions/permissions.yml

@@ -0,0 +1,8 @@
+components:
+  schemas:
+    PermissionClaim:
+      type: string
+      enum: [ SCOPE_user, SCOPE_head_mod ]
+      description: Permission claims used for authorization
+      x-enum-varnames: [ USER, HEAD_MOD ]
+      x-enum-descriptions: [ "User permission", "Head moderator permission" ]