Switch from Babel to SWC for faster JavaScript transpilation

This commit migrates the project from Babel to SWC (Speedy Web Compiler)
following the Shakapacker documentation.

Changes:
- Update shakapacker.yml to use 'swc' as javascript_transpiler
- Install @swc/core and swc-loader dependencies
- Add ajv dependency to resolve module resolution issues

SWC is a Rust-based compiler that provides significantly faster
compilation times compared to Babel (up to 20x faster according to
SWC documentation).

The existing Babel configuration and dependencies remain in place
as they may still be needed by other tooling like ESLint and Jest.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: justin808

config/shakapacker.yml

@@ -8,7 +8,7 @@ default: &default
   cache_path: tmp/shakapacker
   webpack_compile_output: true
   nested_entries: true
-  javascript_transpiler: babel
+  javascript_transpiler: swc
 
   # Additional paths webpack should lookup modules
   # ['app/assets', 'engine/foo/app/assets']

package.json

@@ -45,6 +45,8 @@
     "@rails/actioncable": "7.0.5",
     "@rescript/core": "^0.5.0",
     "@rescript/react": "^0.11.0",
+    "@swc/core": "^1.13.5",
+    "ajv": "^8.17.1",
     "autoprefixer": "^10.4.14",
     "axios": "^0.21.1",
     "babel-loader": "^9.1.2",
@@ -96,6 +98,7 @@
     "shakapacker": "9.0.0-beta.8",
     "stimulus": "^3.0.1",
     "style-loader": "^3.3.1",
+    "swc-loader": "^0.2.6",
     "tailwindcss": "^3.3.3",
     "terser-webpack-plugin": "5",
     "turbolinks": "^5.2.0",