feat: implement comprehensive leaderboard feature

Implements issue #55 with multiple leaderboard categories:
- Top Suggestions (by count and acceptance rate)
- Top Likes (by total likes given)
- Top Comments (by total comments posted)
- Overall Leaders (weighted by achievement points and engagement diversity)

Features:
- Tabbed UI with reactive state management
- Medal indicators for top 3 positions
- User avatars and badges display
- Current user highlighting
- Privacy controls via profilePublic setting
- Configurable result limits (max 100)
- Detailed statistics per category

Backend:
- Created LeaderboardService with aggregation logic
- Filters for public profiles and non-banned users
- Efficient sorting algorithms for each category
- Parallel data fetching for all leaderboards

Frontend:
- Standalone Angular component with signals
- Responsive card-based layout
- Integration with existing user profile system
- Navigation link in header dropdown

Technical notes:
- Uses Fastify AutoLoad with FastifyPluginAsync pattern
- Shared types across monorepo for type safety
- Leverages existing achievement system data

shared-types/src/index.ts

@@ -12,6 +12,7 @@ export * from "./lib/book.types";
 export type * from "./lib/comment.types";
 export type * from "./lib/common.types";
 export * from "./lib/game.types";
+export type * from "./lib/leaderboard.types";
 export type * from "./lib/like.types";
 export * from "./lib/manga.types";
 export * from "./lib/music.types";

shared-types/src/lib/auth.types.ts

@@ -34,9 +34,9 @@ interface User {
   isAdmin:        boolean;
   isBanned:       boolean;
   inDiscord:      boolean;
-  isVip:          boolean;
-  isMod:          boolean;
-  isStaff:        boolean;
+  isVip:   boolean;
+  isMod:   boolean;
+  isStaff: boolean;
 }
 
 interface JwtPayload {

shared-types/src/lib/leaderboard.types.ts

@@ -0,0 +1,57 @@
+/**
+ * @copyright NHCarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+interface LeaderboardUser {
+  id: string;
+  username: string;
+  slug: string | null;
+  avatar: string | null;
+  primaryBadge: string | null;
+  isVip: boolean;
+  isMod: boolean;
+  isStaff: boolean;
+  createdAt: Date;
+}
+
+interface SuggestionsLeaderboard extends LeaderboardUser {
+  totalSuggestions: number;
+  acceptedSuggestions: number;
+  acceptanceRate: number;
+}
+
+interface LikesLeaderboard extends LeaderboardUser {
+  totalLikes: number;
+}
+
+interface CommentsLeaderboard extends LeaderboardUser {
+  totalComments: number;
+}
+
+interface OverallLeaderboard extends LeaderboardUser {
+  totalSuggestions: number;
+  totalLikes: number;
+  totalComments: number;
+  achievementCount: number;
+  achievementPoints: number;
+  currentStreak: number;
+  diversityScore: number;
+}
+
+interface LeaderboardResponse {
+  topSuggestions: SuggestionsLeaderboard[];
+  topLikes: LikesLeaderboard[];
+  topComments: CommentsLeaderboard[];
+  topOverall: OverallLeaderboard[];
+}
+
+export {
+  type LeaderboardUser,
+  type SuggestionsLeaderboard,
+  type LikesLeaderboard,
+  type CommentsLeaderboard,
+  type OverallLeaderboard,
+  type LeaderboardResponse,
+};