Add run-backend.cjs script for starting the backend

scripts/run-backend.cjs

@@ -0,0 +1,44 @@
+const { spawn } = require('child_process')
+const path = require('path')
+
+const projectRoot = path.resolve(__dirname, '..')
+const pythonBin = path.join(projectRoot, 'backend', '.venv', 'bin', 'python')
+
+const env = { ...process.env }
+
+try {
+  const ffmpegPath = require('ffmpeg-static')
+  if (ffmpegPath) {
+    env.HEIMGEIST_FFMPEG_PATH = ffmpegPath
+  }
+} catch (_error) {
+  // Fall back to system PATH if the static binary package is unavailable.
+}
+
+try {
+  const ffprobeStatic = require('ffprobe-static')
+  const ffprobePath = ffprobeStatic && ffprobeStatic.path
+  if (ffprobePath) {
+    env.HEIMGEIST_FFPROBE_PATH = ffprobePath
+  }
+} catch (_error) {
+  // Fall back to system PATH if the static binary package is unavailable.
+}
+
+const child = spawn(
+  pythonBin,
+  ['-m', 'uvicorn', 'backend.main:app', '--host', '127.0.0.1', '--port', '8000', '--reload'],
+  {
+    cwd: projectRoot,
+    env,
+    stdio: 'inherit',
+  }
+)
+
+child.on('exit', (code, signal) => {
+  if (signal) {
+    process.kill(process.pid, signal)
+    return
+  }
+  process.exit(code ?? 0)
+})