fix: enforce the analysis image cap while reading, not after

The OCR and vision dispatchers read the whole page image into a Vec via
storage.get() and only then checked max_image_bytes, so the cap couldn't
bound the read. Stream via get_stream() + safety::accumulate_capped so the
read bails as soon as the running total exceeds the cap.

Bump to 0.124.6.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.124.5",
+  "version": "0.124.6",
   "private": true,
   "type": "module",
   "scripts": {