fix: bump Go to 1.24.13 to resolve stdlib vulnerabilities

Fixes all 13 govulncheck findings (crypto/x509, os/exec, net/http,
etc). Re-enables govulncheck as a hard gate now that stdlib is clean.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: julianknutsen

.github/workflows/ci.yml

@@ -84,7 +84,6 @@ jobs:
         run: go install golang.org/x/vuln/cmd/govulncheck@latest
 
       - name: Go vulnerability check
-        continue-on-error: true
         run: govulncheck ./...
 
       - uses: oven-sh/setup-bun@v2

go.mod

@@ -1,6 +1,6 @@
 module github.com/julianknutsen/wasteland
 
-go 1.24.4
+go 1.24.13
 
 require (
 	github.com/charmbracelet/bubbles v1.0.0