chore: clean up generated files and update gitignore

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

src-tauri/android-signing.gradle.kts

@@ -0,0 +1,34 @@
+// Android signing configuration — reads keystore credentials from external file.
+// This file is kept outside gen/android/ so it survives tauri android init regeneration.
+//
+// Usage: add `apply(from = "../../../android-signing.gradle.kts")` at the bottom of
+//        src-tauri/gen/android/app/build.gradle.kts
+
+import java.util.Properties
+
+val keystorePropertiesFile = java.io.File("/home/msksbr/Android/keystore.properties")
+val keystoreProperties = Properties().apply {
+    if (keystorePropertiesFile.exists()) {
+        keystorePropertiesFile.inputStream().use { load(it) }
+    }
+}
+
+android {
+    signingConfigs {
+        if (keystorePropertiesFile.exists()) {
+            create("release") {
+                storeFile = java.io.File(keystoreProperties["storeFile"] as String)
+                storePassword = keystoreProperties["storePassword"] as String
+                keyAlias = keystoreProperties["keyAlias"] as String
+                keyPassword = keystoreProperties["keyPassword"] as String
+            }
+        }
+    }
+    buildTypes {
+        getByName("release") {
+            if (keystorePropertiesFile.exists()) {
+                signingConfig = signingConfigs.getByName("release")
+            }
+        }
+    }
+}