fix: downgrade go directive to 1.24 and pin GOTOOLCHAIN=local

go.mod specified go 1.25.6 which triggered automatic toolchain download
via Go's toolchain management. Go 1.25 removed the covdata tool, causing
the CI test step to fail with 'go: no such tool covdata'.

Changes:
- go.mod: downgrade 'go 1.25.6' to 'go 1.24' to match CI setup-go version
- ci.yml: add GOTOOLCHAIN=local env at job level to prevent auto-download
  of newer toolchain versions

Fixes CI failure on main branch.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>

.gitea/workflows/ci.yml

@@ -9,6 +9,8 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    env:
+      GOTOOLCHAIN: local
     steps:
       - uses: actions/checkout@v4
 

go.mod

@@ -1,6 +1,6 @@
 module github.com/hits/ExploreDNS
 
-go 1.25.6
+go 1.24.0
 
 require (
 	github.com/miekg/dns v1.1.72