build: bump Go toolchain to go1.25.11 (stdlib CVE fix) (#40)

govulncheck/osv-scan flag the go1.25.10 stdlib CVEs (GO-2026-5038/5039)
on master. Same one-line toolchain bump already landed on api, worker,
and provisioner. No code changes.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mastermanas805

go.mod

@@ -2,7 +2,7 @@ module instant.dev/common
 
 go 1.25.0
 
-toolchain go1.25.10
+toolchain go1.25.11
 
 require (
 	github.com/golang-jwt/jwt/v4 v4.5.2