feat(post-form): live photo editor on entry edit (media API + SortableJS)

Replace the FilePond photo path in edit mode with our own thumbnail grid that
talks straight to the media API (the gpx-manager pattern). Add/delete/reorder
each persist immediately, decoupled from the form's text-field Save:

- Add: HEIC->JPEG client-side, stock POST .../media per file, then ONE reorder
  after the batch (renumber photo-01..NN). On a failed reorder: auto-retry
  (idempotent), else roll the just-uploaded files back so no orphan stock-named
  image breaks cover=first. Upload progress shown per file.
- Delete: inline 'Delete? [Confirm] [Cancel]' (Confirm disabled in flight),
  stock DELETE, then renumber the survivors.
- Reorder: SortableJS drag -> POST /entry/<slug>/photos/order. On failure the
  move reverts to last-known-good; the shown grid never disagrees with disk
  without an inline error.
- Loading + empty states; first cell badged Cover; photo-NN URLs cache-busted
  since reorder reuses them for different bytes.

FilePond is fully decommissioned in edit mode (initPhotoConversion early-returns
under EDIT_MODE): no stale photo_order manifest is posted on text Save, so
cache-on-save can't delete a live-added photo. Create-mode FilePond is untouched.

Adds sortablejs (bundled into js/post via the post-form entry). SVG excluded in
the file-input accept; the server-side SVG block is a documented fast-follow.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

themes/intotheeast/package-lock.json

@@ -12,7 +12,8 @@
         "heic-to": "^1",
         "maplibre-gl": "^4",
         "photoswipe": "^5",
-        "scrollama": "^3"
+        "scrollama": "^3",
+        "sortablejs": "^1.15.7"
       },
       "devDependencies": {
         "esbuild": "^0.21",
@@ -984,6 +985,12 @@
       "integrity": "sha512-PIPwB1kYBnbw/ezvPBJa5dCN5qEwokfpAkI3BmpZWAwcVID4nDf1qH6WV16A2fQaJmsKx0un5S/zhxN+PQeKDQ==",
       "license": "MIT"
     },
+    "node_modules/sortablejs": {
+      "version": "1.15.7",
+      "resolved": "https://registry.npmjs.org/sortablejs/-/sortablejs-1.15.7.tgz",
+      "integrity": "sha512-Kk8wLQPlS+yi1ZEf48a4+fzHa4yxjC30M/Sr2AnQu+f/MPwvvX9XjZ6OWejiz8crBsLwSq8GHqaxaET7u6ux0A==",
+      "license": "MIT"
+    },
     "node_modules/string_decoder": {
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",