fix(deps): update nextjs monorepo to v16

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-node](https://github.com/actions/setup-node) | action | major | `v5` -> `v6` |

---

### Release Notes

<details>
<summary>actions/setup-node (actions/setup-node)</summary>

### [`v6`](https://github.com/actions/setup-node/compare/v5...v6)

[Compare Source](https://github.com/actions/setup-node/compare/v5...v6)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - "every weekend" (UTC), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS4xMjIuMyIsInVwZGF0ZWRJblZlciI6IjQxLjEyMi4zIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6W119-->

Reviewed-on: #18
Co-authored-by: Renovate Bot <renovatebot@schulze.network>
Co-committed-by: Renovate Bot <renovatebot@schulze.network>

.gitea/workflows/lint.yml

@@ -19,7 +19,7 @@ jobs:
         uses: pnpm/action-setup@41ff72655975bd51cab0327fa583b6e92b6d3061 # v4
 
       - name: Setup Node.js
-        uses: actions/setup-node@a0853c24544627f65ddf259abe73b1d18a591444 # v5
+        uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: 24
           cache: "pnpm"

package.json

@@ -31,7 +31,7 @@
     "drizzle-orm": "^0.44.3",
     "lucide-react": "^0.552.0",
     "nanoid": "^5.1.5",
-    "next": "15.5.6",
+    "next": "16.0.1",
     "next-plausible": "^3.12.4",
     "pg": "^8.16.3",
     "pg-native": "^3.5.2",
@@ -44,7 +44,7 @@
   },
   "devDependencies": {
     "@eslint/js": "9.38.0",
-    "@next/eslint-plugin-next": "15.5.6",
+    "@next/eslint-plugin-next": "16.0.1",
     "@tailwindcss/postcss": "4.1.16",
     "@types/node": "24.9.2",
     "@types/pg": "8.15.6",
@@ -54,7 +54,7 @@
     "@typescript-eslint/parser": "8.46.2",
     "drizzle-kit": "0.31.6",
     "eslint": "9.38.0",
-    "eslint-config-next": "15.5.6",
+    "eslint-config-next": "16.0.1",
     "postcss": "8.5.6",
     "prettier": "3.6.2",
     "prettier-plugin-tailwindcss": "0.7.1",