Fix lint errors: add error checks for errcheck linter

- Add error check for JSON response in panic handler
- Remove duplicate defer CloseDB() call (handled in shutdown)
- Add error checks for all WriteField() calls in test files
- Add error checks for CreateFormFile() and Write() calls
- Fix golangci-lint Go 1.25 compatibility by installing from source

middleware/error_handler.go

@@ -43,23 +43,25 @@ func ErrorHandler(c *fiber.Ctx) error {
 // RecoverHandler recovers from panics and returns a proper error response
 func RecoverHandler() fiber.Handler {
 	return func(c *fiber.Ctx) error {
-		defer func() {
-			if r := recover(); r != nil {
-				// Log panic with context
-				log.Printf("Panic recovered: %v | Method: %s | Path: %s | IP: %s",
-					r,
-					c.Method(),
-					c.Path(),
-					c.IP(),
-				)
+			defer func() {
+				if r := recover(); r != nil {
+					// Log panic with context
+					log.Printf("Panic recovered: %v | Method: %s | Path: %s | IP: %s",
+						r,
+						c.Method(),
+						c.Path(),
+						c.IP(),
+					)
 
-				// Return error response
-				c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
-					"success": false,
-					"error":   "Internal Server Error",
-				})
-			}
-		}()
+					// Return error response
+					if err := c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
+						"success": false,
+						"error":   "Internal Server Error",
+					}); err != nil {
+						log.Printf("Failed to send error response: %v", err)
+					}
+				}
+			}()
 
 		return c.Next()
 	}