perf: convert all images to webp, update references

- 77 jpg/png/gif → webp (kept 7 where webp larger)
- public/ assets: 23.3 MB → ~12 MB (~50% smaller)
- 110 image references updated across data files + components
- scripts/convert-to-webp.mjs + scripts/fix-image-refs.mjs added

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/fix-image-refs.mjs

@@ -0,0 +1,70 @@
+import { promises as fs } from 'node:fs';
+import path from 'node:path';
+
+// Build map: relative path that ORIGINALLY existed but now only has .webp
+// Walk /public for .webp files, compute their candidate original ext (.jpg/.png/.gif)
+// If the candidate no longer exists on disk, that's a swap target.
+
+const PUBLIC_ROOT = path.resolve('public');
+const SRC_ROOT = path.resolve('src');
+
+async function walk(dir, out) {
+  const entries = await fs.readdir(dir, { withFileTypes: true });
+  for (const e of entries) {
+    const p = path.join(dir, e.name);
+    if (e.isDirectory()) await walk(p, out);
+    else out.push(p);
+  }
+}
+
+// 1. Find .webp files and detect which original ext is missing
+const all = [];
+await walk(PUBLIC_ROOT, all);
+const webps = all.filter((p) => p.toLowerCase().endsWith('.webp'));
+const existing = new Set(all.map((p) => p.toLowerCase()));
+
+const swaps = []; // { from: /images/foo.jpg, to: /images/foo.webp }
+for (const wp of webps) {
+  const base = wp.slice(0, -5); // strip .webp
+  for (const ext of ['.jpg', '.jpeg', '.png', '.gif']) {
+    const candidate = base + ext;
+    if (!existing.has(candidate.toLowerCase())) {
+      // Candidate gone => it was converted
+      const rel = '/' + path.relative(PUBLIC_ROOT, candidate).split(path.sep).join('/');
+      const relWebp = '/' + path.relative(PUBLIC_ROOT, wp).split(path.sep).join('/');
+      swaps.push({ from: rel, to: relWebp });
+    }
+  }
+}
+
+console.log(`detected ${swaps.length} swap pairs`);
+
+// 2. Walk /src for ts/tsx/js/jsx/json/md/css and apply replacements
+const srcExts = new Set(['.ts', '.tsx', '.js', '.jsx', '.json', '.md', '.css', '.html', '.mjs']);
+const srcFiles = [];
+await walk(SRC_ROOT, srcFiles);
+const targets = srcFiles.filter((p) => srcExts.has(path.extname(p).toLowerCase()));
+
+let totalReplacements = 0;
+let touchedFiles = 0;
+for (const file of targets) {
+  let text = await fs.readFile(file, 'utf8');
+  let count = 0;
+  for (const s of swaps) {
+    if (text.includes(s.from)) {
+      const before = text;
+      text = text.split(s.from).join(s.to);
+      const occurrences = (before.length - text.length) / (s.from.length - s.to.length);
+      count += occurrences;
+    }
+  }
+  if (count > 0) {
+    await fs.writeFile(file, text, 'utf8');
+    totalReplacements += count;
+    touchedFiles++;
+    const rel = path.relative(process.cwd(), file).split(path.sep).join('/');
+    console.log(`UPDATE ${rel}  (${count} swaps)`);
+  }
+}
+console.log('---');
+console.log(`replaced ${totalReplacements} references across ${touchedFiles} files`);