Reduce media bandwidth: compress uploads, add long-lived cache headers, gzip API

- Resize/re-encode every uploaded image server-side (posts, avatars, stories,
  shop products/logo, chat messages) via a shared sharp-based optimizer —
  caps dimensions to what's actually displayed and re-compresses in place,
  cutting a typical raw camera photo by ~90% with no visible quality loss
- Cap uploaded video resolution/bitrate (re-encode only when above 1280px/
  ~2.5Mbps) alongside the existing faststart step; apply faststart+cap to
  story and chat videos too (previously stored completely raw)
- Add long-lived Cache-Control to all /storage static routes so clients stop
  re-downloading unchanged media on every request
- Add gzip/brotli compression for JSON API responses (feed/explore/chat)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

controllers/application/posts/postController.js

@@ -30,6 +30,7 @@ try {
 } catch (error) {
   console.warn('[postController] postVideoProcessing unavailable:', error.message)
 }
+const { optimizeImageFile } = require('../../../utils/imageOptimize')
 
 const createPostValidationRules = () => {
   return [
@@ -89,6 +90,14 @@ const createPost = async (req, res) => {
         ? maskPhoneNumbers(String(caption).trim().slice(0, 2000))
         : null
 
+    // کوچک/فشرده‌کردنِ عکس‌ها قبل از ذخیره — قبل از اینکه مسیرشون توی دیتابیس بره، چون
+    // مسیر (file.path) دست‌نخورده می‌ماند، فقط بایت‌های خودِ فایل جایگزین می‌شوند
+    await Promise.all(
+      files
+        .filter((file) => (file.mimetype || file.type || '').startsWith('image/'))
+        .map((file) => optimizeImageFile(file.path))
+    )
+
     const filePaths = files.map((file) => ({
       path: file.path,
       type: (file.mimetype || file.type || '').startsWith('video/') ? 'video' : 'image'