⬆️ Bump to Next 15 & React 19

```
yarn add \
    next@^15 \
    react@^19 \
    react-dom@^19 \
    @types/react@^19 \
    @types/react-dom@^19
yarn add --dev eslint-config-next@^15
yarn upgrade
sed 's/: JSX.Element//' -i src/components/*.tsx
```

package.json

@@ -10,16 +10,16 @@
     "@fortawesome/free-solid-svg-icons": "^6.7.1",
     "@fortawesome/react-fontawesome": "^0.2.2",
     "@types/node": "^22.10.1",
-    "@types/react": "^18",
-    "@types/react-dom": "^18",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
     "assert": "^2.0.0",
     "axios": "^0.26.0",
     "bootstrap": "^5.3.3",
     "edilkamin": "^1.5.0",
-    "next": "^14",
-    "react": "^18",
+    "next": "^15",
+    "react": "^19",
     "react-bootstrap": "^2.10.6",
-    "react-dom": "^18",
+    "react-dom": "^19",
     "web-vitals": "^2.1.4"
   },
   "scripts": {
@@ -61,7 +61,7 @@
     "@typescript-eslint/eslint-plugin": "^8.17.0",
     "@typescript-eslint/parser": "^8.17.0",
     "eslint": "^9.16.0",
-    "eslint-config-next": "^14",
+    "eslint-config-next": "^15",
     "eslint-config-prettier": "^9.1.0",
     "eslint-plugin-prettier": "^5.2.1",
     "eslint-plugin-simple-import-sort": "^12.1.1",

src/components/Errors.tsx

@@ -3,7 +3,7 @@ import { useContext } from "react";
 import { ErrorContext } from "../context/error";
 import Error from "./Error";
 
-const Errors = (): JSX.Element => {
+const Errors = () => {
   const { errors, setErrors } = useContext(ErrorContext);
   const removeIndex = (index: number) =>
     setErrors(errors.filter((error, i) => i !== index));

src/components/Header.tsx

@@ -5,7 +5,7 @@ import { useIsLoggedIn } from "../utils/hooks";
 import Login from "./Login";
 import Logout from "./Logout";
 
-const Header = (): JSX.Element => (
+const Header = () => (
   <Navbar bg="dark" variant="dark" expand="sm">
     <Container>
       <Navbar.Brand href="/">

src/components/Home.tsx

@@ -11,7 +11,7 @@ import { isValidFireplace } from "../utils/helpers";
 // In our case fireplaces are added by the user and stored to the localStorage.
 const localStorageKey = "fireplaces";
 
-const Home = (): JSX.Element => {
+const Home = () => {
   const getFireplacesLocalStorage = (): string[] =>
     JSON.parse(localStorage.getItem(localStorageKey) || "[]");
 

src/components/Login.tsx

@@ -6,7 +6,7 @@ import { ErrorContext, ErrorType } from "../context/error";
 import { TokenContext } from "../context/token";
 import { setTokenLocalStorage } from "../utils/helpers";
 
-const Login = (): JSX.Element => {
+const Login = () => {
   const [username, setUsername] = useState<string>("");
   const [password, setPassword] = useState<string>("");
   const { setToken } = useContext(TokenContext);

src/components/Logout.tsx

@@ -2,7 +2,7 @@ import { Button } from "react-bootstrap";
 
 import { useLogout } from "../utils/hooks";
 
-const Logout = (): JSX.Element => {
+const Logout = () => {
   // TODO: ideally hit the backend to invalidate the token too
   const logout = useLogout();
   const onLogoutClick = (): void => logout();