feat: connect API to real Lightning node (env vars, healthz, startup warning)

- Add .env.example documenting LNBITS_URL and LNBITS_API_KEY (and all
  other required env vars) so operators know exactly what to set after
  running infrastructure/lnd-init.sh on the droplet.
- Expose lnbits_stub and lnbits_url in GET /api/healthz so operators
  can immediately verify whether the API is connected to a real Lightning
  node or running in simulated stub mode.
- Emit a loud WARN log at production startup when LNBITS_URL /
  LNBITS_API_KEY are absent, pointing to lnd-init.sh for setup.

Infrastructure scripts (setup.sh, lnd-init.sh, sweep.sh, ops.sh,
docker-compose.yml) already cover the full provisioning flow; this
change closes the API-side configuration gap.

Fixes #12

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

artifacts/api-server/src/index.ts

@@ -6,6 +6,7 @@ import { timmyIdentityService } from "./lib/timmy-identity.js";
 import { startEngagementEngine } from "./lib/engagement.js";
 import { relayAccountService } from "./lib/relay-accounts.js";
 import { moderationService } from "./lib/moderation.js";
+import { lnbitsService } from "./lib/lnbits.js";
 
 const rawPort = process.env["PORT"];
 
@@ -25,6 +26,16 @@ attachWebSocketServer(server);
 server.listen(port, () => {
   rootLogger.info("server started", { port });
   rootLogger.info("timmy identity", { npub: timmyIdentityService.npub });
+
+  // Warn loudly in production if Lightning is not connected.
+  if (lnbitsService.stubMode && process.env["NODE_ENV"] === "production") {
+    rootLogger.warn(
+      "LNBITS_URL / LNBITS_API_KEY not set — running in STUB mode. " +
+      "Invoices are simulated in-memory. Set these env vars to connect to a real Lightning node. " +
+      "See infrastructure/lnd-init.sh for setup instructions.",
+      { lnbits_stub: true },
+    );
+  }
   const domain = process.env["REPLIT_DEV_DOMAIN"];
   if (domain) {
     rootLogger.info("public url", { url: `https://${domain}/api/ui` });

artifacts/api-server/src/routes/health.ts

@@ -2,6 +2,7 @@ import { Router, type IRouter, type Request, type Response } from "express";
 import { db, jobs } from "@workspace/db";
 import { sql } from "drizzle-orm";
 import { makeLogger } from "../lib/logger.js";
+import { lnbitsService } from "../lib/lnbits.js";
 
 const router: IRouter = Router();
 const logger = makeLogger("health");
@@ -13,12 +14,24 @@ router.get("/healthz", async (_req: Request, res: Response) => {
     const rows = await db.select({ total: sql<number>`cast(count(*) as int)` }).from(jobs);
     const jobsTotal = Number(rows[0]?.total ?? 0);
     const uptimeS = Math.floor((Date.now() - START_TIME) / 1000);
-    res.json({ status: "ok", uptime_s: uptimeS, jobs_total: jobsTotal });
+    res.json({
+      status: "ok",
+      uptime_s: uptimeS,
+      jobs_total: jobsTotal,
+      lnbits_stub: lnbitsService.stubMode,
+      lnbits_url: lnbitsService.stubMode ? null : process.env["LNBITS_URL"] ?? null,
+    });
   } catch (err) {
     const message = err instanceof Error ? err.message : "Health check failed";
     logger.error("healthz db query failed", { error: message });
     const uptimeS = Math.floor((Date.now() - START_TIME) / 1000);
-    res.status(503).json({ status: "error", uptime_s: uptimeS, error: message });
+    res.status(503).json({
+      status: "error",
+      uptime_s: uptimeS,
+      error: message,
+      lnbits_stub: lnbitsService.stubMode,
+      lnbits_url: lnbitsService.stubMode ? null : process.env["LNBITS_URL"] ?? null,
+    });
   }
 });