chore: initial checkpoint - Tesla Roadtrip planner

- Proactive Grok integration (xAI API + local CLI fallback)
- Real road routing via OSRM (no more bird's-eye lines)
- Heavy structured logging for fast iteration
- Strong sanitization + geocoding + ErrorBoundary (no black screens)
- Playwright E2E tests (API diagnostic + full UI flow)
- scripts/dev.sh for one-command startup
- Clean .env.example + documentation

This is a stable checkpoint before further prompt/UI refinement.

.env.example

@@ -0,0 +1,19 @@
+# Tesla Roadtrip - Environment Configuration
+# Copy this file to .env and fill in the values
+
+# === REQUIRED: xAI API Key for real Grok responses ===
+# Get one at https://console.x.ai
+XAI_API_KEY=xai-YourKeyHere
+
+# === Optional: App configuration ===
+APP_URL=http://localhost:5173
+API_URL=http://localhost:3000
+
+# === Optional: Auth service (from auth.tony.codes) ===
+# Only needed if testing authenticated features locally
+# AUTH_SECRET=your-auth-secret-here
+# AUTH_URL=https://auth.tony.codes
+
+# === Optional: Force local grok CLI (advanced) ===
+# Set to false to always use xAI API instead of local CLI
+# GROK_ENABLED=true