feat: implement comprehensive achievement system with 62 achievements

Adds a complete achievement system with gamification features across all user interactions.

**Database & Types:**
- Add UserAchievement model to track user progress and earned achievements
- Add achievement-related fields to User model (achievementPoints, currentStreak, lastStreakCheck)
- Add ACHIEVEMENT_UNLOCKED audit action type
- Define 62 achievements as TypeScript constants across 5 categories

**Achievement Categories:**
- Suggestions (15): First suggestion through ultimate curator milestones
- Likes (12): First like through legendary fan milestones
- Comments (12): First comment through review legend milestones
- Engagement (15): Login streaks and total activity tracking
- Reports (8): Valid reports and accuracy tracking

**Backend Implementation:**
- Create AchievementService with comprehensive checking logic
- Add achievement route with 6 API endpoints
- Integrate achievement checking into all user interaction points:
  - Suggestions (create + accept)
  - Likes (toggle)
  - Comments (all 6 media types)
  - Login streaks
  - Reports (profile + comment)
- Update UserService to include achievement points in profiles

**Frontend Implementation:**
- Create AchievementService for API communication
- Create achievements page showing all 62 achievements with:
  - Category filtering (All, Suggestions, Likes, Comments, Engagement, Reports)
  - Tier-based styling (Bronze, Silver, Gold, Platinum, Diamond)
  - Progress indicators for in-progress achievements
  - Earned date display for completed achievements
- Add "Recent Achievements" section to user profiles
- Add "🏆 Achievements" link to header navigation
- Only show "View All" link on own profile

**Technical Features:**
- Real-time achievement checking on user actions
- Progress tracking to avoid recalculation
- Points system for gamification
- Tier-based gradient styling
- Leaderboard-ready architecture

Resolves #48

Co-Authored-By: Hikari <hikari@nhcarrigan.com>

api/src/app/routes/achievements/index.ts

@@ -0,0 +1,122 @@
+/**
+ * @copyright 2026 NHCarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import type { FastifyPluginAsync } from "fastify";
+import {
+  ACHIEVEMENT_LIST,
+  ACHIEVEMENTS,
+  AchievementProgress,
+  UserAchievementSummary,
+} from "@library/shared-types";
+import { AchievementService } from "../../services/achievement.service";
+
+const achievementsRoutes: FastifyPluginAsync = async (app) => {
+  const achievementService = new AchievementService();
+
+  /**
+   * Get all achievement definitions (public route).
+   */
+  app.get("/definitions", async () => {
+    return ACHIEVEMENT_LIST;
+  });
+
+  /**
+   * Get a specific achievement definition by key (public route).
+   */
+  app.get<{ Params: { key: string } }>(
+    "/definitions/:key",
+    async (request, reply) => {
+      const { key } = request.params;
+      const achievement = ACHIEVEMENTS[key];
+
+      if (!achievement) {
+        return reply.notFound("Achievement not found");
+      }
+
+      return achievement;
+    },
+  );
+
+  /**
+   * Get current user's achievement summary (authenticated users).
+   */
+  app.get<{ Reply: UserAchievementSummary }>(
+    "/summary",
+    {
+      preValidation: [app.authenticate],
+    },
+    async (request) => {
+      const userId = request.user.id;
+      const summary = await achievementService.getUserAchievementSummary(
+        userId,
+      );
+      return summary;
+    },
+  );
+
+  /**
+   * Get current user's achievement progress (authenticated users).
+   */
+  app.get<{ Reply: AchievementProgress[] }>(
+    "/progress",
+    {
+      preValidation: [app.authenticate],
+    },
+    async (request) => {
+      const userId = request.user.id;
+      const progress = await achievementService.getUserAchievementProgress(
+        userId,
+      );
+      return progress;
+    },
+  );
+
+  /**
+   * Get another user's achievement summary by ID (authenticated users).
+   */
+  app.get<{ Params: { userId: string }; Reply: UserAchievementSummary }>(
+    "/users/:userId/summary",
+    {
+      preValidation: [app.authenticate],
+    },
+    async (request, reply) => {
+      const { userId } = request.params;
+
+      try {
+        const summary = await achievementService.getUserAchievementSummary(
+          userId,
+        );
+        return summary;
+      } catch (error) {
+        return reply.notFound("User not found");
+      }
+    },
+  );
+
+  /**
+   * Get another user's achievement progress by ID (authenticated users).
+   */
+  app.get<{ Params: { userId: string }; Reply: AchievementProgress[] }>(
+    "/users/:userId/progress",
+    {
+      preValidation: [app.authenticate],
+    },
+    async (request, reply) => {
+      const { userId } = request.params;
+
+      try {
+        const progress = await achievementService.getUserAchievementProgress(
+          userId,
+        );
+        return progress;
+      } catch (error) {
+        return reply.notFound("User not found");
+      }
+    },
+  );
+};
+
+export default achievementsRoutes;