chore: set up Biome and CI workflow

.github/workflows/ci.yaml

@@ -0,0 +1,31 @@
+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  ci:
+    name: Lint and Build
+    runs-on: ubuntu-24.04
+
+    defaults:
+      run:
+        working-directory: ./app
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Use Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 22.x
+          cache: npm
+          cache-dependency-path: app/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run lint
+        run: npm run lint
+
+      - name: Build the app
+        run: npm run build

.vscode/settings.json

@@ -0,0 +1,10 @@
+{
+  "biome.configurationPath": "./app/biome.jsonc",
+  "biome.lsp.bin": "./app/node_modules/.bin/biome",
+  "editor.formatOnSave": true,
+  "editor.defaultFormatter": "biomejs.biome",
+  "editor.codeActionsOnSave": {
+    "source.organizeImports.biome": "explicit",
+    "source.fixAll.biome": "explicit"
+  }
+}

app/biome.jsonc

@@ -0,0 +1,60 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.4.10/schema.json",
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true
+  },
+  "files": {
+    "ignoreUnknown": false
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true,
+      "nursery": {
+        "useSortedClasses": {
+          "fix": "safe",
+          "level": "error"
+        }
+      }
+    },
+    "domains": {
+      "next": "recommended",
+      "react": "recommended"
+    }
+  },
+  "css": {
+    "parser": {
+      "tailwindDirectives": true
+    }
+  },
+  "assist": {
+    "enabled": true,
+    "actions": {
+      "source": {
+        "organizeImports": {
+          "level": "on",
+          "options": {
+            "groups": [
+              { "type": false, "source": ["react*", "react/**"] },
+              { "type": false, "source": ":PACKAGE:" },
+              ":BLANK_LINE:",
+              { "type": false, "source": "./lib/**" },
+              { "type": false, "source": ":PATH:" },
+              ":BLANK_LINE:",
+              { "type": false },
+              ":BLANK_LINE:",
+              { "type": true }
+            ]
+          }
+        }
+      }
+    }
+  }
+}