feat: implement user profiles and settings

Add comprehensive user profile system allowing users to showcase
their activity and customize their profiles.

Database Changes:
- Added profile fields to User model: slug, displayName, bio, profilePublic
- Added index on slug field for efficient lookups

API Changes:
- Added GET /users/me endpoint to fetch current user
- Added PUT /users/me endpoint to update user settings
- Added GET /users/profile/:identifier endpoint for public profiles
- Updated UserService with profile methods and statistics
- Modified AuthService to include profile fields in user responses

Frontend Changes:
- Created ProfileComponent to display user profiles with stats
- Created SettingsComponent for profile customization
- Added profile and settings routes
- Updated header dropdown menu with profile links
- Enhanced UserService with profile methods
- Added updateUser method to AuthService

Features:
- Custom profile slugs for clean URLs
- Display names separate from usernames
- User bios (up to 500 characters)
- Public/private profile toggle
- Activity statistics (suggestions, likes, comments, acceptance rate)
- Badge display (Staff, Mod, VIP, Discord Member)
- Beautiful witch-themed styling

Closes #45

apps/frontend/src/app/services/user.service.ts

@@ -9,6 +9,35 @@ import { Observable } from 'rxjs';
 import { ApiService } from './api.service';
 import { User } from '@library/shared-types';
 
+export interface UserProfileResponse {
+  id: string;
+  username: string;
+  displayName?: string;
+  avatar?: string;
+  bio?: string;
+  slug?: string;
+  badges: {
+    isStaff: boolean;
+    isMod: boolean;
+    isVip: boolean;
+    inDiscord: boolean;
+  };
+  stats: {
+    suggestionsCount: number;
+    suggestionsAcceptedCount: number;
+    likesCount: number;
+    commentsCount: number;
+  };
+  createdAt: Date;
+}
+
+export interface UpdateUserSettingsRequest {
+  slug?: string;
+  displayName?: string;
+  bio?: string;
+  profilePublic?: boolean;
+}
+
 @Injectable({
   providedIn: 'root'
 })
@@ -26,4 +55,16 @@ export class UserService {
   unbanUser(userId: string): Observable<User> {
     return this.api.post<User>(`/users/${userId}/unban`, {});
   }
+
+  getMe(): Observable<User> {
+    return this.api.get<User>('/users/me');
+  }
+
+  updateSettings(settings: UpdateUserSettingsRequest): Observable<User> {
+    return this.api.put<User>('/users/me', settings);
+  }
+
+  getProfile(identifier: string): Observable<UserProfileResponse> {
+    return this.api.get<UserProfileResponse>(`/users/profile/${identifier}`);
+  }
 }