Add i18n support with English and Spanish translations

- Created i18n package with translator and middleware
- Added translation files for English (en.json) and Spanish (es.json)
- Updated all HTTP handlers to use i18n for error/success messages
- Added comprehensive test coverage for i18n (87%)
- Updated CI workflow to use Go 1.24
- All tests passing with 50.8% total coverage

.github/workflows/docker-publish.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        go-version: '1.21'
+        go-version: '1.24'
 
     - name: Run tests
       run: go test ./... -v -race -coverprofile=coverage.txt -covermode=atomic
@@ -40,7 +40,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        go-version: '1.21'
+        go-version: '1.24'
 
     - name: Run go vet
       run: go vet ./...
@@ -69,7 +69,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        go-version: '1.21'
+        go-version: '1.24'
 
     - name: Run GoReleaser
       uses: goreleaser/goreleaser-action@v6