chore: prettier format all files, brotli, Sentry release tagging, CI gates

Prettier: auto-formatted 103 files to fix baseline. Prettier check in CI
  is now a hard gate (removed continue-on-error).

Brotli: installed libnginx-mod-http-brotli-filter/static. Enabled in nginx
  with brotli_static on for pre-compressed assets and comp_level 6.

Sentry releases: deploy script now exports VITE_APP_VERSION=<git-short-sha>
  before building so each Sentry release maps to an exact commit.
  CI also passes github.sha as VITE_APP_VERSION.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/components/message/FileHeader.tsx

@@ -48,7 +48,13 @@ export function FileDownloadButton({ filename, url, mimeType, encInfo }: FileDow
       variant={hasError ? 'Critical' : 'SurfaceVariant'}
       size="300"
       radii="300"
-      aria-label={downloading ? 'Downloading...' : hasError ? 'Download failed, click to retry' : 'Download file'}
+      aria-label={
+        downloading
+          ? 'Downloading...'
+          : hasError
+          ? 'Download failed, click to retry'
+          : 'Download file'
+      }
     >
       {downloading ? (
         <Spinner size="100" variant={hasError ? 'Critical' : 'Secondary'} />