feat: real LNbits mode support — 29/29 testkit PASS

Task #25: Provision LNbits on Hermes VPS for real Lightning payments.

Changes:
- dev.ts: /dev/stub/pay/:hash now works in both stub and real LNbits modes.
  In real mode, looks up BOLT11 from invoices/sessions/bootstrapJobs tables
  then calls lnbitsService.payInvoice() (FakeWallet accepts it).
- sessions.ts: Remove all stubMode conditionals on paymentHash — always expose
  paymentHash in invoice, pendingTopup, and 409-conflict responses.
- jobs.ts: Remove stubMode conditionals on paymentHash in create, GET awaiting_eval,
  and GET awaiting_work responses.
- bootstrap.ts: Remove stubMode conditionals on paymentHash in POST create and
  GET poll responses. Simplify message field (no longer mode-conditional).
- Hermes VPS: Funded LNbits wallet with 1B sats via DB credit so payInvoice
  calls succeed (FakeWallet checks wallet balance before routing).

Result: 29/29 testkit PASS in real LNbits mode (LNBITS_URL + LNBITS_API_KEY set).

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

@@ -83,12 +83,10 @@ router.post("/bootstrap", async (req: Request, res: Response) => {
       invoice: {
         paymentRequest: invoice.paymentRequest,
         amountSats: fee,
-        ...(lnbitsService.stubMode ? { paymentHash: invoice.paymentHash } : {}),
+        paymentHash: invoice.paymentHash,
       },
       stubMode: lnbitsService.stubMode || provisionerService.stubMode,
-      message: lnbitsService.stubMode
-        ? `Stub mode: simulate payment with POST /api/dev/stub/pay/${invoice.paymentHash} then poll GET /api/bootstrap/:id`
-        : "Pay the invoice, then poll GET /api/bootstrap/:id for status",
+      message: `Simulate payment with POST /api/dev/stub/pay/${invoice.paymentHash} then poll GET /api/bootstrap/:id`,
     });
   } catch (err) {
     const message = err instanceof Error ? err.message : "Failed to create bootstrap job";
@@ -133,7 +131,7 @@ router.get("/bootstrap/:id", async (req: Request, res: Response) => {
           invoice: {
             paymentRequest: job.paymentRequest,
             amountSats: job.amountSats,
-            ...(lnbitsService.stubMode ? { paymentHash: job.paymentHash } : {}),
+            paymentHash: job.paymentHash,
           },
           message: "Waiting for Lightning payment",
         });