feat(backend): implement comments, image uploads, and data consistency

Implement additional backend features and improve data models:

Comments System:
- Create Comment model with user and post relationships
- Add comments routes: GET /api/posts/:postId/comments (paginated), POST (create), DELETE (own comments)
- Update Post model with commentsCount field
- Emit Socket.IO events for newComment and commentDeleted
- Pagination support for comment lists
- Authorization checks (users can only delete own comments)
- 500 character limit on comments

Image Upload System:
- Implement Cloudinary configuration (config/cloudinary.js)
- Add uploadImage() and deleteImage() helper functions
- Image optimization: max 1000x1000, auto quality, auto format (WebP)
- Integrate image upload in users routes (profile pictures)
- Integrate image upload in posts routes (post images with add/update endpoints)
- File validation: 5MB limit, JPG/PNG/GIF/WebP only
- Automatic image deletion when removing posts/reports

Data Consistency Improvements:
- Add cascade deletes in Street model (remove from user, delete associated tasks)
- Add cascade deletes in Task model (remove from user completedTasks)
- Add cascade deletes in Post model (remove from user posts)
- Update user relationships on save (adoptedStreets, completedTasks, posts, events)
- Add proper indexes for performance (2dsphere for location, compound indexes)
- Add virtual relationships and toJSON configurations

Model Updates:
- Street: Add cascade hooks, location 2dsphere index
- Task: Add cascade hooks, compound indexes for queries
- Post: Add imageUrl, cloudinaryPublicId, commentsCount fields
- Event: Add participants tracking
- Report: Add image upload support
- User: Add earnedBadges virtual, profilePicture, cloudinaryPublicId

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/routes/users.js

@@ -1,21 +1,90 @@
-const express = require('express');
-const User = require('../models/User');
-const auth = require('../middleware/auth');
+const express = require("express");
+const User = require("../models/User");
+const auth = require("../middleware/auth");
+const { asyncHandler } = require("../middleware/errorHandler");
+const { userIdValidation } = require("../middleware/validators/userValidator");
+const { upload, handleUploadError } = require("../middleware/upload");
+const { uploadImage, deleteImage } = require("../config/cloudinary");
 
 const router = express.Router();
 
 // Get user by ID
-router.get('/:id', auth, async (req, res) => {
-  try {
-    const user = await User.findById(req.params.id).populate('adoptedStreets');
+router.get(
+  "/:id",
+  auth,
+  userIdValidation,
+  asyncHandler(async (req, res) => {
+    const user = await User.findById(req.params.id).populate("adoptedStreets");
     if (!user) {
-      return res.status(404).json({ msg: 'User not found' });
+      return res.status(404).json({ msg: "User not found" });
     }
     res.json(user);
-  } catch (err) {
-    console.error(err.message);
-    res.status(500).send('Server error');
-  }
-});
+  }),
+);
+
+// Upload profile picture
+router.post(
+  "/profile-picture",
+  auth,
+  upload.single("image"),
+  handleUploadError,
+  asyncHandler(async (req, res) => {
+    if (!req.file) {
+      return res.status(400).json({ msg: "No image file provided" });
+    }
+
+    const user = await User.findById(req.user.id);
+    if (!user) {
+      return res.status(404).json({ msg: "User not found" });
+    }
+
+    // Delete old profile picture if exists
+    if (user.cloudinaryPublicId) {
+      await deleteImage(user.cloudinaryPublicId);
+    }
+
+    // Upload new image to Cloudinary
+    const result = await uploadImage(
+      req.file.buffer,
+      "adopt-a-street/profiles",
+    );
+
+    // Update user with new profile picture
+    user.profilePicture = result.url;
+    user.cloudinaryPublicId = result.publicId;
+    await user.save();
+
+    res.json({
+      msg: "Profile picture updated successfully",
+      profilePicture: user.profilePicture,
+    });
+  }),
+);
+
+// Delete profile picture
+router.delete(
+  "/profile-picture",
+  auth,
+  asyncHandler(async (req, res) => {
+    const user = await User.findById(req.user.id);
+    if (!user) {
+      return res.status(404).json({ msg: "User not found" });
+    }
+
+    if (!user.cloudinaryPublicId) {
+      return res.status(400).json({ msg: "No profile picture to delete" });
+    }
+
+    // Delete image from Cloudinary
+    await deleteImage(user.cloudinaryPublicId);
+
+    // Remove from user
+    user.profilePicture = undefined;
+    user.cloudinaryPublicId = undefined;
+    await user.save();
+
+    res.json({ msg: "Profile picture deleted successfully" });
+  }),
+);
 
 module.exports = router;