fix: resolve pnpm monorepo Metro bundling + add GitHub release workflow

- Add babel-preset-expo as explicit devDep (fixes "Cannot find module" crash)
- Configure metro.config.js with watchFolders for pnpm workspace root
- Bump expo devDep to ~54.0.34, remove duplicate deps/devDeps
- Add .github/workflows/release.yml: signed APK on git tag vX.Y.Z

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

artifacts/postiz-mobile/metro.config.js

@@ -1,3 +1,16 @@
 const { getDefaultConfig } = require("expo/metro-config");
+const path = require("path");
 
-module.exports = getDefaultConfig(__dirname);
+const projectRoot = __dirname;
+const workspaceRoot = path.resolve(projectRoot, "../..");
+
+const config = getDefaultConfig(projectRoot);
+
+// pnpm monorepo: expose workspace root node_modules to Metro
+config.watchFolders = [workspaceRoot];
+config.resolver.nodeModulesPaths = [
+  path.resolve(projectRoot, "node_modules"),
+  path.resolve(workspaceRoot, "node_modules"),
+];
+
+module.exports = config;