feat: self-contained Docker installer with web setup wizard

- settings.ts: persistent settings.json in data volume (survives restarts)
- /api/setup: POST to save API_BASE_URL, API_KEY, WEB_PASSWORD, WEBHOOK_SECRET
- /setup: web-based setup wizard for first-time configuration
- /api/health: JSON health check endpoint for Docker healthcheck
- api.ts: dynamic API_BASE_URL/API_KEY resolution from settings
- login route: fallback WEB_PASSWORD from settings.json
- middleware: /setup and /api/setup are public paths
- Dockerfile: HEALTHCHECK instruction
- docker-compose.yml: healthcheck + optional .env file
- .env.example: full documentation of all env vars
- install.sh: single-command VPS installer (clone, build, run)

src/app/api/setup/route.ts

@@ -0,0 +1,28 @@
+import { saveSettings, isConfigured, allSettings } from "@/lib/settings"
+
+export async function GET() {
+  const configured = isConfigured()
+  return Response.json({ configured })
+}
+
+export async function POST(req: Request) {
+  const body = await req.json()
+
+  const allowed = [
+    "API_BASE_URL",
+    "API_KEY",
+    "WEB_PASSWORD",
+    "WEBHOOK_SECRET",
+  ]
+
+  const toSave: Record<string, string> = {}
+  for (const key of allowed) {
+    if (body[key] !== undefined) {
+      toSave[key] = String(body[key])
+    }
+  }
+
+  saveSettings(toSave)
+
+  return Response.json({ ok: true, configured: isConfigured() })
+}