perf: enable lazy loading for avatars and thumbnails

Added `loading="lazy"` and `decoding="async"` attributes to dynamically created `<img>` elements in:
- `js/historyView.js` (avatars)
- `js/ui/subscriptionHistoryController.js` (channel icons)
- `js/searchView.js` (added `decoding="async"`)
- `js/ui/profileModal/ProfileDirectMessageRenderer.js` (attachment previews, avatars)
- `js/ui/profileModalController.js` (attachment previews, saved profile avatars)

This reduces initial page load impact and bandwidth usage by deferring off-screen image loading.

Co-authored-by: PR0M3TH3AN <[email protected]>

scripts/measure_lazy_loading.mjs

@@ -0,0 +1,49 @@
+import fs from 'fs';
+import path from 'path';
+
+const filesToCheck = [
+  'js/historyView.js',
+  'js/ui/subscriptionHistoryController.js',
+  'js/searchView.js',
+  'js/ui/profileModal/ProfileDirectMessageRenderer.js',
+  'js/ui/profileModalController.js'
+];
+
+let totalImages = 0;
+let missingLazy = 0;
+let missingAsync = 0;
+
+filesToCheck.forEach(file => {
+  const content = fs.readFileSync(file, 'utf8');
+  const lines = content.split('\n');
+
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    if (line.includes('createElement("img")') || line.includes("createElement('img')")) {
+        totalImages++;
+
+        // simple heuristic: look ahead next 20 lines for attributes
+        let chunk = lines.slice(i, i + 20).join('\n');
+
+        // Check for variable name
+        const match = line.match(/(?:const|let|var)\s+(\w+)\s*=/);
+        const varName = match ? match[1] : null;
+
+        if (varName) {
+            if (!chunk.includes(`${varName}.loading = "lazy"`)) {
+                missingLazy++;
+                console.log(`[${file}] Missing loading="lazy" for ${varName} at line ${i+1}`);
+            }
+            if (!chunk.includes(`${varName}.decoding = "async"`)) {
+                missingAsync++;
+                console.log(`[${file}] Missing decoding="async" for ${varName} at line ${i+1}`);
+            }
+        }
+    }
+  }
+});
+
+console.log('--- Results ---');
+console.log(`Total images found: ${totalImages}`);
+console.log(`Missing loading="lazy": ${missingLazy}`);
+console.log(`Missing decoding="async": ${missingAsync}`);