Add appeal and login functionality structure

Introduces initial structure for appeal and login forms in both the frontend and backend. New controllers, APIs, and components were created, but functionality has not been fully implemented yet. This serves as a foundation for future development of these features.

backend/src/main/java/com/alttd/altitudeweb/controllers/application/AppealController.java

@@ -0,0 +1,28 @@
+package com.alttd.altitudeweb.controllers.application;
+
+import com.alttd.altitudeweb.api.AppealsApi;
+import com.alttd.altitudeweb.model.AppealResponseDto;
+import com.alttd.altitudeweb.model.DiscordAppealDto;
+import com.alttd.altitudeweb.model.MinecraftAppealDto;
+import com.alttd.altitudeweb.model.UpdateMailDto;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.server.ResponseStatusException;
+
+public class AppealController implements AppealsApi {
+
+    @Override
+    public ResponseEntity<MinecraftAppealDto> submitDiscordAppeal(DiscordAppealDto discordAppealDto) {
+        throw new ResponseStatusException(HttpStatusCode.valueOf(501), "Discord appeals are not yet supported");
+    }
+
+    @Override
+    public ResponseEntity<AppealResponseDto> submitMinecraftAppeal(MinecraftAppealDto minecraftAppealDto) {
+        throw new ResponseStatusException(HttpStatusCode.valueOf(501), "Minecraft appeals are not yet supported");
+    }
+
+    @Override
+    public ResponseEntity<AppealResponseDto> updateMail(UpdateMailDto updateMailDto) {
+        throw new ResponseStatusException(HttpStatusCode.valueOf(501), "Updating mail is not yet supported");
+    }
+}

backend/src/main/java/com/alttd/altitudeweb/controllers/login/LoginController.java

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+package com.alttd.altitudeweb.controllers.login;
+
+import com.alttd.altitudeweb.api.LoginApi;
+import com.alttd.altitudeweb.model.AddLoginDto;
+import com.alttd.altitudeweb.model.LoginDataDto;
+import com.alttd.altitudeweb.model.LoginResultDto;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.server.ResponseStatusException;
+
+public class LoginController implements LoginApi {
+
+    @Override
+    public ResponseEntity<Void> addLogin(AddLoginDto addLoginDto) {
+        throw new ResponseStatusException(HttpStatusCode.valueOf(501), "Adding login is not yet supported");
+    }
+
+    @Override
+    public ResponseEntity<LoginResultDto> login(LoginDataDto loginDataDto) {
+        throw new ResponseStatusException(HttpStatusCode.valueOf(501), "Logging in is not yet supported");
+    }
+}