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/public/manifest.json

@@ -1,25 +1,40 @@
 {
-    "short_name":  "JobTrack",
-    "name":  "JobTrack — Job Application Tracker",
-    "icons":  [
-                  {
-                      "src":  "favicon.ico",
-                      "sizes":  "64x64 32x32 24x24 16x16",
-                      "type":  "image/x-icon"
-                  },
-                  {
-                      "src":  "logo192.png",
-                      "type":  "image/png",
-                      "sizes":  "192x192"
-                  },
-                  {
-                      "src":  "logo512.png",
-                      "type":  "image/png",
-                      "sizes":  "512x512"
-                  }
-              ],
-    "start_url":  ".",
-    "display":  "standalone",
-    "theme_color":  "#0b1224",
-    "background_color":  "#0b1224"
+  "short_name": "Jobbjakt",
+  "name": "Jobbjakt — Job Application Tracker",
+  "description": "Track and manage your job applications, tailor CVs, and stay on top of follow-ups.",
+  "id": "/",
+  "scope": "/",
+  "start_url": ".",
+  "display": "standalone",
+  "orientation": "portrait-primary",
+  "categories": ["productivity", "business"],
+  "theme_color": "#15803d",
+  "background_color": "#0b1224",
+  "icons": [
+    {
+      "src": "favicon.ico",
+      "sizes": "64x64 32x32 24x24 16x16",
+      "type": "image/x-icon"
+    },
+    {
+      "src": "logo192.png",
+      "type": "image/png",
+      "sizes": "192x192",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "logo512.png",
+      "type": "image/png",
+      "sizes": "512x512",
+      "purpose": "any maskable"
+    }
+  ],
+  "share_target": {
+    "action": "/",
+    "method": "GET",
+    "params": {
+      "url": "add",
+      "text": "addtext"
+    }
+  }
 }