fix: use rust:slim-trixie for JDK 21 and latest Rust, trim CI paths

- Switch to Debian Trixie base for native JDK 21 and latest Rust
- Remove Adoptium APT repo workaround
- Only trigger Android CI on src-tauri/ and build config changes

Dockerfile.android

@@ -1,13 +1,10 @@
-FROM rust:1.87-bookworm
+FROM rust:slim-trixie
 
-# Java 21 via Adoptium APT repo (Bookworm only has JDK 17)
+# Java 21 + build tools
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    unzip wget curl ca-certificates gnupg && \
-    wget -qO- https://packages.adoptium.net/artifactory/api/gpg/key/public | gpg --dearmor -o /usr/share/keyrings/adoptium.gpg && \
-    echo "deb [signed-by=/usr/share/keyrings/adoptium.gpg] https://packages.adoptium.net/artifactory/deb bookworm main" > /etc/apt/sources.list.d/adoptium.list && \
-    apt-get update && apt-get install -y --no-install-recommends temurin-21-jdk && \
+    openjdk-21-jdk-headless unzip wget curl ca-certificates && \
     rm -rf /var/lib/apt/lists/*
-ENV JAVA_HOME=/usr/lib/jvm/temurin-21-jdk-amd64
+ENV JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64
 
 # Android SDK
 ENV ANDROID_HOME=/opt/android-sdk