Add initial project structure with core functionality for book and stationery uploads

- Created main application entry point in `main.go`.
- Added configuration management in `config/config.go` and tests in `config/config_test.go`.
- Implemented handlers for book and stationery uploads in `handlers/book.go` and `handlers/stationery.go`, including validation logic.
- Established database connection and services in `services/database.go` and `services/book_service.go`.
- Defined models for books and stationery in `models/book.go` and `models/stationery.go`.
- Set up Firebase integration for image uploads in `services/firebase.go`.
- Created migration scripts for database schema in `migrations/001_create_tables.sql` and subsequent updates.
- Added CORS and error handling middleware.
- Included comprehensive tests for handlers, services, and utilities.
- Documented API endpoints and usage in `README.md` and migration instructions in `migrations/README.md`.
- Introduced `.gitignore` to exclude unnecessary files and directories.
- Added Go module support with `go.mod` and `go.sum` files.
- Implemented utility functions for slug generation and validation in `utils/slug.go` and `utils/validation.go`.

middleware/error_handler.go

@@ -0,0 +1,66 @@
+package middleware
+
+import (
+	"log"
+
+	"github.com/gofiber/fiber/v2"
+)
+
+// ErrorHandler is a global error handler middleware
+func ErrorHandler(c *fiber.Ctx) error {
+	// Call next middleware/handler
+	err := c.Next()
+
+	// If no error, return
+	if err == nil {
+		return nil
+	}
+
+	// Log error with context
+	log.Printf("Error: %v | Method: %s | Path: %s | IP: %s",
+		err,
+		c.Method(),
+		c.Path(),
+		c.IP(),
+	)
+
+	// Check if error is a Fiber error
+	code := fiber.StatusInternalServerError
+	message := "Internal Server Error"
+
+	if e, ok := err.(*fiber.Error); ok {
+		code = e.Code
+		message = e.Message
+	}
+
+	// Return structured error response
+	return c.Status(code).JSON(fiber.Map{
+		"success": false,
+		"error":   message,
+	})
+}
+
+// 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(),
+				)
+
+				// Return error response
+				c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
+					"success": false,
+					"error":   "Internal Server Error",
+				})
+			}
+		}()
+
+		return c.Next()
+	}
+}