Add on-device debug logging: file capture + share (for real-session testing)

- fileLogger: append redacted API requests/responses + app events to an on-device
  log file (persists across restarts); the client's logSink now writes to it
- Diagnostics screen (Account > Diagnostics): toggle recording, Share log file
  (expo-sharing), clear. StartSession logs the session attempt/result explicitly.
- Lets a real parking session be captured while away from a computer, then shared.

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

package-lock.json

@@ -21,11 +21,13 @@
         "@react-navigation/native-stack": "^7.0.0",
         "expo": "~53.0.0",
         "expo-constants": "~17.0.0",
+        "expo-file-system": "~18.1.11",
         "expo-linking": "~7.0.0",
         "expo-localization": "~16.0.0",
         "expo-location": "~18.0.0",
         "expo-notifications": "~0.29.0",
         "expo-secure-store": "~14.0.0",
+        "expo-sharing": "~13.1.5",
         "expo-status-bar": "~2.0.0",
         "parksmarter-client": "*",
         "react": "19.0.0",
@@ -4939,6 +4941,15 @@
         "expo": "*"
       }
     },
+    "node_modules/expo-sharing": {
+      "version": "13.1.5",
+      "resolved": "https://registry.npmjs.org/expo-sharing/-/expo-sharing-13.1.5.tgz",
+      "integrity": "sha512-X/5sAEiWXL2kdoGE3NO5KmbfcmaCWuWVZXHu8OQef7Yig4ZgHFkGD11HKJ5KqDrDg+SRZe4ISd6MxE7vGUgm4w==",
+      "license": "MIT",
+      "peerDependencies": {
+        "expo": "*"
+      }
+    },
     "node_modules/expo-status-bar": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/expo-status-bar/-/expo-status-bar-2.0.1.tgz",