fix(db): add missing apiKeys columns + restore ApiExplorerModal export

- schema.js: add createdAt/allowedModels to apiKeys, bump SCHEMA_VERSION 3->4
- shared/components/index.js: restore ApiExplorerModal barrel export (was replaced by TagInput)
- combos: tag support, repo + api + page updates

xd:/browser

@@ -0,0 +1 @@
+{"action":"run","name":"combos","code":"async (page) => { await page.setCookie(...require(\"fs\").readFileSync(\"/tmp/9r-cookies.txt\",\"utf8\").split(\"\\n\").filter(l=>!l.startsWith(\"#\")&&l.trim()).map(l=>{const p=l.split(\"\\t\"); return {name:p[5], value:p[6], domain:\"localhost\", path:\"/\"};})); await page.goto(\"http://localhost:20128/dashboard/combos\", {waitUntil:\"networkidle0\"}); return await page.evaluate(()=>document.body.innerText.substring(0,1500)); }","i":"load combos with auth"}