Add GitHub Actions CI, wire ESLint, lock in Caddy

CI pipeline with parallel jobs for fast feedback:
- typecheck, lint, unit tests, build run in parallel
- e2e tests run after build
- Playwright artifacts uploaded on failure

ESLint wired into both apps with sensible defaults:
- underscore-prefixed unused vars allowed
- root package.json marked as type: module

Architecture updated: Caddy as reverse proxy with auto HTTPS.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/journal/package.json

@@ -7,7 +7,8 @@
     "dev": "react-router dev",
     "build": "react-router build",
     "start": "react-router-serve ./build/server/index.js",
-    "typecheck": "react-router typegen && tsc"
+    "typecheck": "react-router typegen && tsc",
+    "lint": "eslint ."
   },
   "dependencies": {
     "@trails-cool/ui": "workspace:*",