Migrates the existing upload/format-select/quality/convert logic from
the old single-file App.jsx into a router shell (/ -> /fr//en/) with a
shared Layout (header, language switcher, dark-mode toggle, footer).
Tool logic itself is unchanged, only restyled into cards.
Part of the Ombrora Convert redesign (Task 2/5).
Also fixes a Windows-specific bug in worker.js and cleanup.js: the
"run only if executed directly" guard compared import.meta.url against
`file://${process.argv[1]}`, which never matches on Windows (backslash
path separators, missing extra slash before the drive letter). main()
silently never ran, so the worker process started and exited
immediately without ever polling. Caught during this task's manual
verification of the full upload-convert-download flow. Fixed with
node:url's pathToFileURL, which builds a correct file:// URL cross-platform.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
anthony
