Give the app a sidebar, and the media library a screen of its own

[pallaoro]

The editor had no navigation at all — one top header — and the global footage
library sat in a tab inside a single composition. The library is not
per-composition state, so it becomes a screen of its own next to the gallery.

What changed

• /media route rendering the existing MediaPanel, moved rather than
  rewritten. The tab is gone from the composition editor; RendersPanel is
  genuinely per-composition and stays.
• <AppNav> from @clawnify/app defines the navigation once. Opened
  directly it paints the app's own 275px rail; embedded in the Clawnify
  dashboard it paints nothing and hands the same list to the dashboard's
  sidebar, so there is never a second nav.
  • Compositions is home, so it is the brand row rather than a listed item;
    Media is the single row.
  • The Media badge is the asset count. That is why the asset list moved up
    to <App>: MediaPanel now reads it and asks for a reload, so uploading
    or deleting a file moves the number in both sidebars in the same tick —
    no extra endpoint, no polling.
• reportLocation() on every router change, so a dashboard reload lands back
  on the screen you were on.

Two details worth a second look

• The rail override block in styles.css keeps only geometry inside
  @media (min-width: 768px). aside.cn-nav outranks the SDK's own
  .cn-nav, and specificity is resolved before source order, so an unguarded
  width: 275px would be a 275px column on a 390px phone that no ordering
  could fix. Paint and type stay global, and they map onto this app's tokens
  (the SDK's fallbacks assume a --sunken this app calls --surface-sunken,
  and a --primary that is ink here).
• The shell takes a definite h-dvh rather than a min-height. With a
  min-height every descendant height is indefinite, and the editor's
  resizable group — which sizes off a percentage height — collapses to a
  4px seam below 768px. Verified against main to confirm it was my
  regression and not pre-existing.

Verified

• vite build clean, tsc --noEmit clean.
• Rendered at two viewports against a live dev server: 1280px → rail is a
  275px column, 800px tall, no page overflow; 390px → rail is a full-width
  390 x 45 horizontal strip, scrollWidth === clientWidth, no sideways scroll.
• /media renders the library (dropzone, seeded asset, assets/<key> paths)
  with the Media row active; / still renders the gallery; the composition
  editor still opens with its timeline/compose/renders switcher and a
  full-height panel group at both widths.