chore: clean up generated files and update gitignore

- remove api-docs.json from version control
- add src-tauri/gen/ to gitignore

src-tauri/gen/android/app/.gitignore

@@ -0,0 +1,6 @@
+/src/main/**/generated
+/src/main/jniLibs/**/*.so
+/src/main/assets/tauri.conf.json
+/tauri.build.gradle.kts
+/proguard-tauri.pro
+/tauri.properties