feat: installable PWA with mobile share-target capture

- Corrected manifest (Jobbjakt branding, matching green theme, maskable
  icons, description/categories/scope/id).
- share_target (GET) maps a shared url/link into the same /?add= capture
  flow the bookmarklet uses, so mobile 'Share -> Jobbjakt' pre-fills Add
  Job.
- resolveCaptureUrl helper (tested) extracts the link from add or from a
  link embedded in shared text; App uses it and strips the params.
- Deliberately no offline service worker: the app deploys frequently and
  an aggressive cache would risk stale builds (documented in README).
- 4 unit tests; build compiles.

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

job-tracker-ui/src/captureUrl.ts

@@ -0,0 +1,10 @@
+// Resolves the quick-capture URL from query params produced by the bookmarklet (`add`)
+// or the PWA share-target (a link in `add`, or embedded in shared `addtext`).
+export function resolveCaptureUrl(search: string): string | null {
+  const params = new URLSearchParams(search);
+  const add = params.get("add");
+  if (add) return add;
+  const addText = params.get("addtext");
+  if (addText) return addText.match(/https?:\/\/\S+/)?.[0] ?? null;
+  return null;
+}