fix: reliable first-message send, QR routing, auto-lock recovery

Fixes reported by testers and found in an app review:

- First message right after install no longer fails. Before the app
  finished registering with the relay, the outgoing message could crash on
  a null delivery address. The profile field is now optional and the send
  path throws a clear "still connecting, try again shortly" error while
  registration completes in the background.
- The QR code and share link now appear only once the delivery address is
  ready. Previously a link generated before the first connection lacked
  routing, so the other side could not send the first message. The screen
  now shows a connecting state and reactively swaps in the QR when ready.
- Incomplete contact links are rejected on import instead of failing at
  first send, with a clear prompt to ask for a fresh link.
- Auto-lock no longer silences the app: after locking and unlocking,
  messaging is restarted (it previously stayed dead until app restart).
- Group messages are marked failed on a non-per-member send error instead
  of hanging in the "sending" state forever.
- Hardened the relay client against a rare duplicate connection when
  toggling Tor or locking mid-connect, and fromShareString now rejects a
  delivery address of the wrong length.
- Pin unifiedpush below 6.2.0 to drop the webcrypto dependency (its native
  framework lacks LC_ENCRYPTION_INFO and blocked the iOS upload).
- Skip Android release lint (network dependency check hangs on the build
  host and adds no value for a Flutter app).

app/pubspec.lock

@@ -193,14 +193,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "8.12.3"
-  change_case:
-    dependency: transitive
-    description:
-      name: change_case
-      sha256: e41ef3df58521194ef8d7649928954805aeb08061917cf658322305e61568003
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.2.0"
   characters:
     dependency: transitive
     description:
@@ -924,14 +916,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.17.6"
-  native_toolchain_cmake:
-    dependency: transitive
-    description:
-      name: native_toolchain_cmake
-      sha256: "9960e1e926ec210a3ba6fe61720d48e1dd6cbab00d05890a6e147ee45b7e47c5"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.6"
   objective_c:
     dependency: transitive
     description:
@@ -1196,46 +1180,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.5.2"
-  screen_retriever:
-    dependency: transitive
-    description:
-      name: screen_retriever
-      sha256: "42cc3b402a0f67d2455a0d067553d0f13453f6a008d98eababf8b63958d506bd"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.1"
-  screen_retriever_linux:
-    dependency: transitive
-    description:
-      name: screen_retriever_linux
-      sha256: "2a476f1a5538065bc5badf376cfdc83d6ecf07d77eb2391b9c2bff5a76970048"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.1"
-  screen_retriever_macos:
-    dependency: transitive
-    description:
-      name: screen_retriever_macos
-      sha256: b5abb900fcb86614ff10b738b34e37b9e1d03b0447280668e2bc8a98bdc7bd59
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.1"
-  screen_retriever_platform_interface:
-    dependency: transitive
-    description:
-      name: screen_retriever_platform_interface
-      sha256: "3af22d926bedf20c2caa308eea376776451a3af125919ce072e56525fded8901"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.1"
-  screen_retriever_windows:
-    dependency: transitive
-    description:
-      name: screen_retriever_windows
-      sha256: c44b38a4c4bab34af259180a70a4eee1e29384e7b82e627c9faa68afcdab2e73
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.1"
   share_plus:
     dependency: "direct main"
     description:
@@ -1413,42 +1357,26 @@ packages:
     dependency: "direct main"
     description:
       name: unifiedpush
-      sha256: "8ed9767f750a1dc6159a77e2171641d0cb825dc87682d1ce1b8618689b79f58e"
+      sha256: b52a0eff848d0446b9d521e0ad2f7bc76c4dda88d0f6ac0a79f1765ccfe37939
       url: "https://pub.dev"
     source: hosted
-    version: "6.2.0"
+    version: "6.1.0"
   unifiedpush_android:
     dependency: transitive
     description:
       name: unifiedpush_android
-      sha256: "2e6684e0a1a39ad8d6c7bc0d197954d50686acb1b1a7614b18ab0e0126f5492a"
+      sha256: "2af6a09a5fb9fdd97b61e704a587e88abcdb5f7ee2aea9a2c35e80159f9d586d"
       url: "https://pub.dev"
     source: hosted
-    version: "3.4.1"
-  unifiedpush_linux:
-    dependency: transitive
-    description:
-      name: unifiedpush_linux
-      sha256: c062d5eedd1cec70bcd33270cc4e01ae0ff6501f33d471167c06b34a968adfeb
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.0"
+    version: "3.3.1"
   unifiedpush_platform_interface:
     dependency: transitive
     description:
       name: unifiedpush_platform_interface
-      sha256: "83372bc8d794b8b12ef6993b518d7be907dcfc2191bdf6de0ece5c4445d89880"
+      sha256: "5aa3eefc2699e4d8db6d723f0cfdfb56ac850487549a0b3b83574f4a89f33aab"
       url: "https://pub.dev"
     source: hosted
-    version: "4.0.0"
-  unifiedpush_storage_interface:
-    dependency: transitive
-    description:
-      name: unifiedpush_storage_interface
-      sha256: b8d423a4695efc616aa21d8ab48fb5ef99d6288c68b56282b8faac1579ceabd9
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.0"
+    version: "3.1.0"
   universal_io:
     dependency: transitive
     description:
@@ -1585,14 +1513,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.3"
-  webcrypto:
-    dependency: transitive
-    description:
-      name: webcrypto
-      sha256: "9885ed99a846191542dd6ca820c83a098117df56be57453832233a3fef68f3f2"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.6.1"
   webdriver:
     dependency: transitive
     description:
@@ -1601,14 +1521,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.1.0"
-  webpush_encryption:
-    dependency: transitive
-    description:
-      name: webpush_encryption
-      sha256: "5b83272b91acda6ae515fcd980c94f06bf413702282497c5a68f5dfc64fed27f"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.1"
   win32:
     dependency: transitive
     description:
@@ -1617,14 +1529,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "5.15.0"
-  window_manager:
-    dependency: transitive
-    description:
-      name: window_manager
-      sha256: "7eb6d6c4164ec08e1bf978d6e733f3cebe792e2a23fb07cbca25c2872bfdbdcd"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.5.1"
   xdg_directories:
     dependency: transitive
     description: