Replace manual backend config with auto JWT auth

Device auto-registers on first launch using hardcoded backend URL
and anon key (MarksAuth.swift). 90-day JWT stored in UserDefaults,
refreshed transparently. No settings fields needed — ClaudeService
is always active and non-optional throughout the app.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.runner

@@ -0,0 +1,14 @@
+{
+  "WARNING": "This file is automatically generated by act-runner. Do not edit it manually unless you know what you are doing. Removing this file will cause act runner to re-register as a new runner.",
+  "id": 3,
+  "uuid": "68105c19-5047-4a36-9342-2877162f169e",
+  "name": "marks-runner",
+  "token": "1e23b24d76fc51bd9b442349a780c38fceced821",
+  "address": "https://git.magicive.com",
+  "labels": [
+    "macos:host",
+    "arm64:host",
+    "ios:host",
+    "xcode:host"
+  ]
+}