Add F-Droid metadata, store listing, iOS encryption declaration

- F-Droid metadata: mobile/fdroid/metadata/info.hasdo.taskteam.yml
- Store listing for APKPure/Aurora: mobile/store-listing/README.md
- iOS ITSAppUsesNonExemptEncryption=false in app.json
- Mixed content audit: clean (no HTTP URLs in frontend code)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mobile/app.json

@@ -13,7 +13,10 @@
     },
     "ios": {
       "supportsTablet": true,
-      "bundleIdentifier": "info.hasdo.taskteam"
+      "bundleIdentifier": "info.hasdo.taskteam",
+      "infoPlist": {
+        "ITSAppUsesNonExemptEncryption": false
+      }
     },
     "android": {
       "adaptiveIcon": {