build(android): release signing + mirror/JDK setup; native-feel CSS

- Release signing via android/keystore.properties (git-ignored); build.gradle
  signs release builds when the props file is present, stays unsigned otherwise.
- android/mirror-init.gradle: injects the myket.ir Maven mirror into every
  project's buildscript (dl.google.com is unreachable here) and pins Build-Tools
  to the installed 36.0.0. Build with:
    gradlew assembleRelease bundleRelease -I mirror-init.gradle
  (JAVA_HOME must point at a JDK 21 — Capacitor 8 compiles against Java 21.)
- gitignore keystores, keystore.properties, and /dist artifacts.
- Native-app feel: kill tap-highlight, long-press callout, and stray text
  selection (inputs/messages opt back in); touch-action: manipulation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -25,6 +25,12 @@
 # production
 /build
 
+# built mobile artifacts (APK/AAB) + release signing secrets
+/dist
+/android/keystore.properties
+*.jks
+*.keystore
+
 # misc
 .DS_Store
 *.pem