refactor: consolidate lang into constants, rename services to email

- Merge lang package into constants (add IsValidLang, ValidateLang, AllLangs)
- Rename internal/services to internal/email for consistency with pdf package
- Rename types to avoid redundancy: EmailService→Service, EmailConfig→Config
- Update all imports and references across codebase
- Delete internal/lang directory (functions moved to constants)

internal/handlers/cv_text_test.go

@@ -8,14 +8,10 @@ import (
 )
 
 // TestPlainText tests the PlainText handler
-// NOTE: This test requires running from project root due to template path resolution
-// Run with: go test ./internal/handlers/ -run TestPlainText -v
-// Or skip in CI: go test ./internal/handlers/ -run TestPlainText -short
 func TestPlainText(t *testing.T) {
-	// Skip if running in short mode (CI) - requires project root
-	if testing.Short() {
-		t.Skip("Skipping PlainText test - requires running from project root")
-	}
+	// Change to project root for template path resolution
+	cleanup := chDirToProjectRoot(t)
+	defer cleanup()
 
 	handler := newTestCVHandler(t, "localhost:8080", nil)
 
@@ -122,12 +118,10 @@ func TestPlainText(t *testing.T) {
 }
 
 // TestPlainTextDownloadFilename tests that download filename is correctly formatted
-// NOTE: This test requires running from project root due to template path resolution
 func TestPlainTextDownloadFilename(t *testing.T) {
-	// Skip if running in short mode (CI) - requires project root
-	if testing.Short() {
-		t.Skip("Skipping PlainTextDownloadFilename test - requires running from project root")
-	}
+	// Change to project root for template path resolution
+	cleanup := chDirToProjectRoot(t)
+	defer cleanup()
 
 	handler := newTestCVHandler(t, "localhost:8080", nil)