🧪 test: add comprehensive BDD test suite for user authentication

Added BDD test scenarios covering:
- User registration with validation
- Successful and failed authentication
- Admin authentication with master password
- JWT token generation and validation
- Password reset workflow
- Edge cases and error handling

BDD Features:
- 20+ authentication scenarios
- JWT validation edge cases
- Password reset security scenarios
- Input validation tests
- Error response verification

BDD Infrastructure:
- Step definitions for authentication workflows
- Test server with user management endpoints
- JWT parsing and validation utilities
- Common step patterns for reuse

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

pkg/bdd/testserver/client.go

@@ -115,6 +115,59 @@ func (c *Client) CustomRequest(method, path string, body interface{}) (*http.Res
 	return resp, nil
 }
 
+// RequestWithHeader allows setting custom headers for the request
+func (c *Client) RequestWithHeader(method, path string, body interface{}, headers map[string]string) error {
+	url := c.server.GetBaseURL() + path
+
+	var reqBody io.Reader
+	if body != nil {
+		// Handle different body types
+		switch b := body.(type) {
+		case []byte:
+			reqBody = bytes.NewReader(b)
+		case string:
+			reqBody = strings.NewReader(b)
+		case map[string]string:
+			jsonBody, err := json.Marshal(b)
+			if err != nil {
+				return fmt.Errorf("failed to marshal JSON body: %w", err)
+			}
+			reqBody = bytes.NewReader(jsonBody)
+		default:
+			return fmt.Errorf("unsupported body type: %T", body)
+		}
+	}
+
+	req, err := http.NewRequest(method, url, reqBody)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+
+	// Set content type for JSON bodies
+	if body != nil && reqBody != nil {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	// Set custom headers
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	c.lastResp = resp
+	c.lastBody, err = io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("failed to read response body: %w", err)
+	}
+
+	return nil
+}
+
 func (c *Client) ExpectResponseBody(expected string) error {
 	if c.lastResp == nil {
 		return fmt.Errorf("no response received")
@@ -139,3 +192,10 @@ func (c *Client) GetLastResponse() *http.Response {
 func (c *Client) GetLastBody() []byte {
 	return c.lastBody
 }
+
+func (c *Client) GetLastStatusCode() int {
+	if c.lastResp == nil {
+		return 0
+	}
+	return c.lastResp.StatusCode
+}