generate index.html's absolute URLs from PUBLIC_URL

index.html hardcoded the deployment's domain in eight places, so every instance
had to carry its own edit of the file — the only thing separating the rezio
branch from master.

The tags genuinely need absolute URLs. OpenGraph is fetched standalone by
crawlers, and Bun's HTML bundler treats a root-relative href as an asset to
resolve on disk, failing the build with "Could not resolve: /favicon.ico" —
external URLs are the only form it passes through untouched.

Bun's HTML import offers no substitution hook, so scripts/gen-index.ts swaps
__PUBLIC_URL__ for the value in .env and writes index.gen.html, which the server
imports. index.html is the tracked template and is now identical on every
deployment; index.gen.html is gitignored. predev/prestart run the generator, and
it is idempotent so --watch does not loop.

Substituting also fixes the manifest: an absolute URL puts its fetch in CORS
mode, which failed whenever the hardcoded domain was not the serving origin.

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

.gitignore

@@ -42,3 +42,6 @@ src/config.ts
 # Playwright
 playwright/
 .wwebjs_cache/
+
+# generated from index.html by scripts/gen-index.ts
+src/apps/officer-web/index.gen.html