fix: upload progress bar never repainted (missing from mediabrowser fingerprint)

mediaUpload changes on every XHR tick but wasn't part of the mediabrowser
zone's ViewBus fingerprint, so real ticks hashed identically to the last
paint and were skipped -- the bar only ever appeared to update via some
unrelated repaint (e.g. clicking a thumbnail changes mediaPreviewId, which
IS tracked).

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

movie_editor/frontend/view_bus.js

@@ -176,6 +176,10 @@
       projects: st.projects?.length,
       media: st.mediaBin?.length,
       mediaPreview: st.mediaPreviewId,
+      // The upload progress bar/percent live in this zone and change on every XHR
+      // progress tick without touching mediaBin's length -- without this the drop
+      // zone never repaints and looks stale for the whole upload.
+      upload: st.mediaUpload,
       // Continuity pin renders on gallery cards (📌 button state + thumb badge).
       pin: st.project?.continuity_settings?.identity_pin_ref,
       // Reference marks render the same way (R button + numbered badge), and their ORDER