feat(auth): Implement database-backed user authentication and

persistence

This commit introduces a major architectural change by replacing the
previous hardcoded user and data system with a robust, database-driven
approach. It lays the foundation for persistent data storage for all
application models.

Key Changes:

- **Database Integration:** - Added `GORM` and `SQLite` for the database
layer. - The database is now initialized and migrated on application
startup. - Configuration is managed through environment variables
(`DATABASE`, `USERS_FILE`).

- **User Authentication & Management:** - The login endpoint
(`/api/token`) now authenticates users against the database. - JWT
claims are now populated with real user data (`id`, `username`,
`is_superuser`). - Implemented a system to seed the database with
initial users from a `users.json` file.

- **New User API Endpoints:** - `GET /api/users`: Retrieves a list of
all users (superuser access required). - `GET /api/users/user`: Fetches
the data for the currently authenticated user based on their JWT.

- **Data Model Overhaul:** - Refactored all data models (`User`,
`Category`, `Operation`, `Subcategory`) to include GORM tags,
relationships, and a `BaseModel` with auto-generated UUIDs for primary
keys. - Separated user-related structs into `User` (database model),
`AuthRequest` (login payload), and `UserResponse` (safe API response).

- **Middleware & Routing:** - Improved JWT error handling for clearer
client-side messages. - Added a new middleware to allow passing the JWT
in the request body for more flexible client integration.

backend/internal/operation/GetAllOperation.go

@@ -8,12 +8,13 @@ import (
 func GetAllOperation() ([]model.Operation, error) {
 	return []model.Operation{
 		{
-			ID:       "1",
-			Title:    "Operation 1",
-			Amount:   100,
-			Category: "Category 1",
-			SubCategory: model.Subcategory{
-				ID:    "1",
+			Title:  "Operation 1",
+			Amount: 100,
+			Category: model.Category{
+				Title: "category 1",
+				Type:  "income",
+			},
+			Subcategory: model.Subcategory{
 				Title: "subcategory",
 			},
 			Date: "2022-01-01T00:00:00Z",
@@ -21,30 +22,35 @@ func GetAllOperation() ([]model.Operation, error) {
 			Icon: "😀",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-01-02T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-01-02T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     time.Now().Format(time.RFC3339),
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: time.Now().Format(time.RFC3339),
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "1",
-			Title:    "Operation 1",
-			Amount:   100,
-			Category: "Category 1",
-			SubCategory: model.Subcategory{
-				ID:    "1",
+			Title:  "Operation 1",
+			Amount: 100,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Subcategory: model.Subcategory{
 				Title: "subcategory",
 			},
 			Date: "2022-01-02T00:00:00Z",
@@ -52,22 +58,26 @@ func GetAllOperation() ([]model.Operation, error) {
 			Icon: "😀",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-06-02T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-06-02T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-06-22T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-06-22T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 	}, nil
 }