Fix review findings #2: template escaping, ops.sh on node, fee NaN guard

1. Escape ${i} bash loop vars in TypeScript template literal (provisioner.ts)
   - Four occurrences: Bitcoin RPC wait, LND REST wait, macaroon wait, LNbits wait
   - Changed ${i}x5s → \${i}x5s so TypeScript doesn't try to resolve 'i'
   - Confirmed: tsc reports no errors in provisioner.ts after fix

2. Install minimal ops.sh on provisioned node via cloud-init (provisioner.ts)
   - Cloud-init step 15 writes /opt/timmy-node/ops.sh with sync/lnd/lnbits/logs cmds
   - Uses single-quoted heredoc (<<'OPSSH') to prevent bash expanding ops.sh's
     own $CMD / ${1:-help} / ${2:-bitcoin} variables during cloud-init execution
   - chmod +x applied after write
   - sync command: docker exec bitcoin bitcoin-cli getblockchaininfo | jq summary
   - lnd, lnbits, logs subcommands also included

3. Update nextSteps to reference installed ops.sh (bootstrap.ts)
   - "Monitor Bitcoin sync (takes 1-2 weeks to reach 100%): bash /opt/timmy-node/ops.sh sync"
   - All other nextSteps reference files/URLs actually present on the node

4. Harden BOOTSTRAP_FEE_SATS parsing against NaN (pricing.ts)
   - parseInt on empty/invalid env var → NaN
   - Added Number.isFinite(rawFee) && rawFee > 0 guard → falls back to 10_000
   - Same pattern could be applied to other numeric env vars as follow-up

End-to-end verified: POST → pay → provisioning → ready with correct nextSteps

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

@@ -169,7 +169,7 @@ router.get("/bootstrap/:id", async (req: Request, res: Response) => {
           nextSteps: [
             `SSH into your node using the private key above: ssh -i <key_file> root@${job.nodeIp ?? "<nodeIp>"}`,
             "Read your node credentials: cat /root/node-credentials.txt",
-            "Monitor Bitcoin sync (takes 1-2 weeks): docker exec bitcoin bitcoin-cli getblockchaininfo",
+            "Monitor Bitcoin sync (takes 1-2 weeks to reach 100%): bash /opt/timmy-node/ops.sh sync",
             "Once sync is complete, fund your LND wallet, then open LNbits to create your wallet and get the API key",
             "Set LNBITS_URL and LNBITS_API_KEY in your Timmy deployment to enable payment processing",
           ],