Phase 3: Express backend, SQLite persistence, auto-save

- server/db.ts: sql.js with migration system (hex_maps, hexes, hex_features)
- server/routes/maps.ts: CRUD for hex maps
- server/routes/hexes.ts: Bulk hex upsert, region load, sparse storage
- server/index.ts: Express 5, CORS, tile serving, SPA fallback
- src/data/api-client.ts: Frontend HTTP client for all API endpoints
- src/main.ts: Auto-save with 1s debounce, load map state on startup
- Port 3002 (Kiepenkerl uses 3001)
- Graceful fallback when API unavailable (works without server too)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/routes/maps.ts

@@ -0,0 +1,85 @@
+import { Router } from 'express';
+import { getDb, saveDb } from '../db.js';
+
+const router = Router();
+
+// List all maps
+router.get('/', (_req, res) => {
+  const db = getDb();
+  const rows = db.exec('SELECT * FROM hex_maps ORDER BY updated_at DESC');
+  if (rows.length === 0) {
+    res.json([]);
+    return;
+  }
+  const maps = rows[0].values.map(row => rowToMap(rows[0].columns, row));
+  res.json(maps);
+});
+
+// Get single map
+router.get('/:id', (req, res) => {
+  const db = getDb();
+  const rows = db.exec('SELECT * FROM hex_maps WHERE id = ?', [req.params.id]);
+  if (rows.length === 0 || rows[0].values.length === 0) {
+    res.status(404).json({ error: 'Map not found' });
+    return;
+  }
+  res.json(rowToMap(rows[0].columns, rows[0].values[0]));
+});
+
+// Create map
+router.post('/', (req, res) => {
+  const db = getDb();
+  const { name, image_width, image_height, tile_url, min_zoom, max_zoom, hex_size, origin_x, origin_y } = req.body;
+  db.run(
+    `INSERT INTO hex_maps (name, image_width, image_height, tile_url, min_zoom, max_zoom, hex_size, origin_x, origin_y)
+     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+    [name ?? 'Untitled', image_width ?? 8000, image_height ?? 12000,
+     tile_url ?? '/tiles/{z}/{x}/{y}.jpg', min_zoom ?? 0, max_zoom ?? 6,
+     hex_size ?? 48, origin_x ?? 0, origin_y ?? 0],
+  );
+  const idRows = db.exec('SELECT last_insert_rowid()');
+  const id = idRows[0].values[0][0];
+  saveDb();
+  res.status(201).json({ id });
+});
+
+// Update map
+router.put('/:id', (req, res) => {
+  const db = getDb();
+  const { name, hex_size, origin_x, origin_y } = req.body;
+  const sets: string[] = [];
+  const params: any[] = [];
+
+  if (name !== undefined) { sets.push('name = ?'); params.push(name); }
+  if (hex_size !== undefined) { sets.push('hex_size = ?'); params.push(hex_size); }
+  if (origin_x !== undefined) { sets.push('origin_x = ?'); params.push(origin_x); }
+  if (origin_y !== undefined) { sets.push('origin_y = ?'); params.push(origin_y); }
+
+  if (sets.length === 0) {
+    res.status(400).json({ error: 'No fields to update' });
+    return;
+  }
+
+  sets.push("updated_at = datetime('now')");
+  params.push(req.params.id);
+
+  db.run(`UPDATE hex_maps SET ${sets.join(', ')} WHERE id = ?`, params);
+  saveDb();
+  res.json({ ok: true });
+});
+
+// Delete map
+router.delete('/:id', (req, res) => {
+  const db = getDb();
+  db.run('DELETE FROM hex_maps WHERE id = ?', [req.params.id]);
+  saveDb();
+  res.json({ ok: true });
+});
+
+function rowToMap(columns: string[], values: any[]) {
+  const obj: any = {};
+  columns.forEach((col, i) => { obj[col] = values[i]; });
+  return obj;
+}
+
+export default router;