feat(auth): implement JWT authentication flow

This commit implements a full-stack authentication system using JWT.

On the backend, a new login endpoint `/api/token` is created. It
validates credentials and issues a signed JWT. A JWT middleware is added
to the server configuration to protect sensitive API endpoints like
`/api/category` and `/api/operation`. Configuration is now managed via a
`wallet.conf` file, loaded at startup.

On the frontend, this enables a complete authentication lifecycle: - A
new `/login` page allows users to enter their credentials. - A
`PrivateRoute` component wraps protected pages, redirecting
unauthenticated users to the login page. - API calls to protected
resources now include the `Authorization: Bearer <token>` header. - A
logout function is added to clear user session data.

refactor(ui): enhance history and category views

This commit also introduces major UI improvements.

The History modal has been completely redesigned. Operations are no
longer displayed as a flat list but are now grouped into tabs for Daily,
Weekly, Monthly, and Yearly views, providing a much clearer overview of
transactions.

The Categories modal now separates categories into "Incomes" and
"Expenses" tabs, reflecting the changes in the backend data model.

backend/internal/operation/GetAllOperation.go

@@ -1,6 +1,9 @@
 package operation
 
-import "backend/model"
+import (
+	"backend/model"
+	"time"
+)
 
 func GetAllOperation() ([]model.Operation, error) {
 	return []model.Operation{
@@ -26,5 +29,45 @@ func GetAllOperation() ([]model.Operation, error) {
 			Type:     "expense",
 			Icon:     "😂",
 		},
+		{
+			ID:       "2",
+			Title:    "Operation 2",
+			Amount:   200,
+			Category: "Category 2",
+			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: "subcategory",
+			},
+			Date: "2022-01-02T00:00:00Z",
+			Type: "income",
+			Icon: "😀",
+		},
+		{
+			ID:       "2",
+			Title:    "Operation 2",
+			Amount:   200,
+			Category: "Category 2",
+			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:     "😂",
+		},
 	}, nil
 }