Add LOD backfill script for existing images without asset_key

Queries DB for images where asset_key IS NULL, downloads each from
MinIO, generates LOD tiers (thumb/medium/full), uploads them, and
updates the DB record. Skips LOD for videos, SVGs, and GIFs. Logs
per-image progress and continues on individual failures.

backend/scripts/backfill-lod.js

@@ -0,0 +1,118 @@
+#!/usr/bin/env node
+/**
+ * Backfill LOD tiers for existing images that don't have an asset_key yet.
+ *
+ * For each image where asset_key IS NULL:
+ *   - Videos: set asset_key, upload single file under asset_key/full{ext}
+ *   - SVG/GIF: set asset_key, upload single file under asset_key/full{ext}
+ *   - Other images: generate 3 LOD tiers (thumb, medium, full), upload all, set asset_key
+ *
+ * Usage: node scripts/backfill-lod.js
+ */
+
+const path = require('path');
+
+// Load .env from backend root if present
+try {
+  require('dotenv').config({ path: path.join(__dirname, '..', '.env') });
+} catch {
+  // dotenv not required
+}
+
+const { db } = require('../db');
+const { minioClient, putBuffer, MINIO_BUCKET, MIME_TO_EXT } = require('../minio');
+const { generateLOD } = require('../services/lod-generator');
+
+/**
+ * Download an object from MinIO into a Buffer.
+ */
+function downloadFromMinio(objectName) {
+  return new Promise((resolve, reject) => {
+    const chunks = [];
+    minioClient.getObject(MINIO_BUCKET, objectName, (err, stream) => {
+      if (err) return reject(err);
+      stream.on('data', (chunk) => chunks.push(chunk));
+      stream.on('end', () => resolve(Buffer.concat(chunks)));
+      stream.on('error', reject);
+    });
+  });
+}
+
+/**
+ * Process a single image record.
+ */
+async function processImage(image) {
+  const { id, board_id, minio_path, mime_type, media_type } = image;
+  const assetKey = `boards/${board_id}/${id}`;
+  const ext = MIME_TO_EXT[mime_type] || '.bin';
+
+  // Download original from MinIO
+  const buffer = await downloadFromMinio(minio_path);
+
+  // Videos: single file, no LOD
+  if (media_type === 'video') {
+    const fullPath = `${assetKey}/full${ext}`;
+    await putBuffer(fullPath, buffer, mime_type);
+    db.prepare("UPDATE images SET asset_key = ?, minio_path = ? WHERE id = ?")
+      .run(assetKey, fullPath, id);
+    return;
+  }
+
+  // SVG and GIF: single file, no LOD processing
+  if (mime_type === 'image/svg+xml' || mime_type === 'image/gif') {
+    const fullPath = `${assetKey}/full${ext}`;
+    await putBuffer(fullPath, buffer, mime_type);
+    db.prepare("UPDATE images SET asset_key = ?, minio_path = ? WHERE id = ?")
+      .run(assetKey, fullPath, id);
+    return;
+  }
+
+  // Standard images: generate 3 LOD tiers
+  const lod = await generateLOD(buffer, ext);
+
+  await Promise.all([
+    putBuffer(`${assetKey}/thumb${lod.thumb.ext}`, lod.thumb.buffer,
+      lod.thumb.ext === '.webp' ? 'image/webp' : mime_type),
+    putBuffer(`${assetKey}/medium${lod.medium.ext}`, lod.medium.buffer,
+      lod.medium.ext === '.webp' ? 'image/webp' : mime_type),
+    putBuffer(`${assetKey}/full${lod.full.ext}`, lod.full.buffer, mime_type),
+  ]);
+
+  const fullPath = `${assetKey}/full${lod.full.ext}`;
+  db.prepare("UPDATE images SET asset_key = ?, minio_path = ?, width = COALESCE(width, ?), height = COALESCE(height, ?) WHERE id = ?")
+    .run(assetKey, fullPath, lod.full.width, lod.full.height, id);
+}
+
+async function main() {
+  // Find all images without an asset_key
+  const images = db.prepare("SELECT * FROM images WHERE asset_key IS NULL").all();
+
+  if (images.length === 0) {
+    console.log('[backfill-lod] No images need backfilling. All done.');
+    return;
+  }
+
+  console.log(`[backfill-lod] Found ${images.length} image(s) to backfill.\n`);
+
+  let success = 0;
+  let failed = 0;
+
+  for (const image of images) {
+    const label = `${image.id} (${image.filename}, ${image.mime_type})`;
+    try {
+      await processImage(image);
+      success++;
+      console.log(`  \u2713 ${label}`);
+    } catch (err) {
+      failed++;
+      console.error(`  \u2717 ${label} — ${err.message}`);
+    }
+  }
+
+  console.log(`\n[backfill-lod] Done. ${success} succeeded, ${failed} failed out of ${images.length} total.`);
+}
+
+main().catch((err) => {
+  console.error('[backfill-lod] Fatal error:', err);
+  process.exit(1);
+});