Update Go version to 1.25 and test matrix to 1.24 and 1.25

Upgrade from outdated Go 1.21/1.22 to the currently supported versions (1.24 and 1.25). This ensures the project benefits from latest security patches and language features.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <[email protected]>

Author: ceritium

.github/workflows/release.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.21'
+          go-version: '1.25'
           cache: true
 
       - name: Run GoReleaser

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.21', '1.22']
+        go-version: ['1.24', '1.25']
 
     steps:
     - uses: actions/checkout@v4

go.mod

@@ -1,6 +1,6 @@
 module github.com/stacktodate/stacktodate-cli
 
-go 1.21
+go 1.25
 
 require (
 	github.com/spf13/cobra v1.8.0