feat: add backend server and service modules

Includes HTTP server with auth, static file serving, and API routes.
Services cover GPU monitoring, quota checking, Gitea repo listing,
workspace management, agent task orchestration, and settings persistence.

src/services/gpu.js

@@ -0,0 +1,49 @@
+import { runProcess } from '../process.js';
+
+const NVIDIA_QUERY = [
+  '--query-gpu=index,name,memory.used,memory.total,utilization.gpu',
+  '--format=csv,noheader,nounits'
+];
+
+function parseGpuLine(line) {
+  const [index, name, memoryUsed, memoryTotal, utilization] = line.split(',').map((part) => part.trim());
+  return {
+    index: Number(index),
+    name,
+    memoryUsedMiB: Number(memoryUsed),
+    memoryTotalMiB: Number(memoryTotal),
+    gpuUtilizationPercent: Number(utilization)
+  };
+}
+
+export function parseNvidiaSmiCsv(output) {
+  return output
+    .split('\n')
+    .map((line) => line.trim())
+    .filter(Boolean)
+    .map(parseGpuLine)
+    .filter((gpu) => Number.isFinite(gpu.index));
+}
+
+export async function collectGpuStatus(config) {
+  const hosts = config.gpuHosts || [];
+  const checks = hosts.map(async (host) => {
+    const result = await runProcess('ssh', [
+      '-o', 'BatchMode=yes',
+      '-o', `ConnectTimeout=${Math.max(1, Math.ceil((config.sshTimeoutMs || 10000) / 1000))}`,
+      host,
+      'nvidia-smi',
+      ...NVIDIA_QUERY
+    ], { timeoutMs: config.sshTimeoutMs || 10000 });
+
+    return {
+      host,
+      ok: result.ok,
+      checkedAt: new Date().toISOString(),
+      gpus: result.ok ? parseNvidiaSmiCsv(result.stdout) : [],
+      error: result.ok ? null : result.stderr || result.stdout || 'Unable to query GPU status.'
+    };
+  });
+
+  return Promise.all(checks);
+}