perf: lazy async image decoding + max-height to prevent scroll freeze

ROOT CAUSE: Articles from sites like onemileatatime.com serve WebP
images with .jpeg extensions. WebKit attempts JPEG decode, fails,
retries as WebP — the retry loop blocks the compositor thread during
scroll, causing ~1s freezes per image.

FIX 1 — Image attributes (ArticleHTMLBuilder.optimizeImages):
Regex injects loading="lazy" decoding="async" on all <img> tags
that don't already have loading= set. This tells WebKit to:
- decode images off the main/compositor thread (decoding=async)
- only decode when approaching viewport (loading=lazy)

FIX 2 — CSS max-height:
img { max-height: 600px; object-fit: contain; }
Limits decoded image buffer size. A 1200x900 image still displays
at full width but WebKit doesn't need to composite oversized tiles.

Both fixes are content-rendering optimizations only — no changes
to WKWebView architecture, scrolling model, or layout system.

Also marked Atmos Rewards articles as unread for testing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ios/Platform/Platform/Features/Reader/Views/ArticleView.swift

@@ -156,7 +156,7 @@ enum ArticleHTMLBuilder {
     .article-meta {
         font-size: 13px; color: #8B6914; line-height: 1.4;
     }
-    img { max-width: 100%; height: auto; border-radius: 8px; margin: 12px 0; }
+    img { max-width: 100%; height: auto; max-height: 600px; object-fit: contain; border-radius: 8px; margin: 12px 0; }
     a { color: #8B6914; }
     h1, h2, h3, h4 { line-height: 1.3; margin-top: 24px; margin-bottom: 8px; }
     pre, code { background: #f5f0e8; border-radius: 6px; padding: 2px 6px; font-size: 15px; overflow-x: auto; }
@@ -214,9 +214,27 @@ enum ArticleHTMLBuilder {
         <h1 class="article-title">\(titleHTML)</h1>
         <div class="article-meta">\(meta)</div>
         </div>
-        <div id="article-body">\(body)</div>
+        <div id="article-body">\(optimizeImages(body))</div>
         </body>
         </html>
         """
     }
+
+    /// Add loading="lazy" and decoding="async" to all <img> tags.
+    /// This tells WebKit to decode images off the main thread and
+    /// only when they approach the viewport, preventing scroll freezes
+    /// from large/mismatched-type images (e.g. WebP served as .jpeg).
+    private static let imgTagRegex = try! NSRegularExpression(
+        pattern: #"<img(?![^>]*loading=)([^>]*)>"#,
+        options: .caseInsensitive
+    )
+
+    private static func optimizeImages(_ html: String) -> String {
+        let range = NSRange(html.startIndex..., in: html)
+        return imgTagRegex.stringByReplacingMatches(
+            in: html,
+            range: range,
+            withTemplate: #"<img loading="lazy" decoding="async"$1>"#
+        )
+    }
 }