Bump tsdown from 0.14.0 to 0.21.7

Bumps [tsdown](https://github.com/rolldown/tsdown) from 0.14.0 to 0.21.7.
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.14.0...v0.21.7)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.21.7
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/astro-tunnel/package.json

@@ -35,7 +35,7 @@
     "@types/node": "24.10.1",
     "@typescript/native-preview": "7.0.0-dev.20251203.1",
     "astro": "5.16.6",
-    "tsdown": "0.14.0"
+    "tsdown": "0.21.7"
   },
   "peerDependencies": {
     "astro": ">=4.0.0"