fix(lint): add error checking for resp.Body.Close in dcr/client.go

Add proper error handling for deferred resp.Body.Close() calls in
DCR client Register() and RequestTokens() methods. Use defer func
pattern to check and handle (but not fail on) close errors.

This fixes errcheck violations in production code.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: platinummonkey

pkg/auth/dcr/client.go

@@ -73,7 +73,11 @@ func (c *Client) Register(redirectURI string, scopes []string) (*types.ClientCre
 	if err != nil {
 		return nil, fmt.Errorf("failed to send registration request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			// Log but don't fail - response already read
+		}
+	}()
 
 	// Read response
 	respBody, err := io.ReadAll(resp.Body)
@@ -150,7 +154,11 @@ func (c *Client) requestTokens(data url.Values) (*types.TokenSet, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to send token request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			// Log but don't fail - response already read
+		}
+	}()
 
 	// Read response
 	respBody, err := io.ReadAll(resp.Body)