feat(activity-log): integrate logging across all endpoints (Phase 3)

Added comprehensive activity logging to 14 integration points:

Auth Controller (4 actions):
- AUTH_REGISTER: User registration
- AUTH_LOGIN: User login
- AUTH_VERIFY_EMAIL: Email verification (token & code)
- AUTH_PASSWORD_RESET: Password reset

Events Routes (2 actions):
- EVENT_CHECKIN: User checks into event
- EVENT_LEAVE: User leaves event

Socket Handlers (3 actions):
- EVENT_JOIN_CHAT: User joins event chat room
- EVENT_LEAVE_CHAT: User leaves event chat room
- CHAT_JOIN_ROOM: User joins private match chat

Matches Routes (3 actions):
- MATCH_CREATE: Match request created
- MATCH_ACCEPT: Match request accepted
- MATCH_REJECT: Match request rejected/cancelled

Admin Routes (1 action + security):
- ADMIN_MATCHING_RUN: Admin runs matching algorithm
- Added requireAdmin middleware to all admin routes

All logs include:
- User ID and username (denormalized)
- IP address (X-Forwarded-For aware)
- Action type and resource ID
- HTTP method and path (or SOCKET for WebSocket)
- Contextual metadata (event slugs, match IDs, etc.)

Fire-and-forget pattern ensures logging never blocks requests.

backend/src/socket/index.js

@@ -1,6 +1,7 @@
 const { Server } = require('socket.io');
 const { verifyToken } = require('../utils/auth');
 const { prisma } = require('../utils/db');
+const { ACTIONS, log: activityLog } = require('../services/activityLog');
 
 // Track active users in each event room
 const activeUsers = new Map(); // eventId -> Set of { socketId, userId, username, avatar }
@@ -202,6 +203,20 @@ function initializeSocket(httpServer) {
           username: socket.user.username,
           avatar: socket.user.avatar,
         });
+
+        // Log join event chat activity
+        activityLog({
+          userId: socket.user.id,
+          username: socket.user.username,
+          ipAddress: socket.handshake.address,
+          action: ACTIONS.EVENT_JOIN_CHAT,
+          resource: `event:${eventId}`,
+          method: 'SOCKET',
+          path: 'join_event_room',
+          metadata: {
+            eventSlug: slug,
+          },
+        });
       } catch (error) {
         console.error('Join event room error:', error);
         socket.emit('error', { message: 'Failed to join room' });
@@ -236,6 +251,20 @@ function initializeSocket(httpServer) {
 
       console.log(`👤 ${socket.user.username} left event room ${socket.currentEventSlug}`);
 
+      // Log leave event chat activity
+      activityLog({
+        userId: socket.user.id,
+        username: socket.user.username,
+        ipAddress: socket.handshake.address,
+        action: ACTIONS.EVENT_LEAVE_CHAT,
+        resource: `event:${eventId}`,
+        method: 'SOCKET',
+        path: 'leave_event_room',
+        metadata: {
+          eventSlug: socket.currentEventSlug,
+        },
+      });
+
       // Clear current event data
       socket.currentEventId = null;
       socket.currentEventRoom = null;
@@ -349,6 +378,20 @@ function initializeSocket(httpServer) {
             where: { id: parseInt(matchId) },
             data: updateData,
           });
+
+          // Log join match room activity
+          activityLog({
+            userId: socket.user.id,
+            username: socket.user.username,
+            ipAddress: socket.handshake.address,
+            action: ACTIONS.CHAT_JOIN_ROOM,
+            resource: `match:${matchId}`,
+            method: 'SOCKET',
+            path: 'join_match_room',
+            metadata: {
+              matchId: parseInt(matchId),
+            },
+          });
         }
       } catch (error) {
         console.error('Join match room error:', error);