build: add Biome formatter and linter with development tooling

- Add Biome configuration with consistent code style rules
- Configure formatter with single quotes, semicolons, and 100 line width
- Setup linter with recommended rules and custom overrides
- Add Husky pre-commit hook for lint-staged
- Add VSCode settings for Biome integration
- Update package.json with Biome scripts and dependencies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: ericyangpan

.husky/pre-commit

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+npx lint-staged

.vscode/extensions.json

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+{
+  "recommendations": ["biomejs.biome", "streetsidesoftware.code-spell-checker"]
+}

.vscode/settings.json

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+{
+  "editor.formatOnSave": true,
+  "editor.defaultFormatter": "biomejs.biome",
+  "editor.codeActionsOnSave": {
+    "source.fixAll.biome": "explicit"
+  },
+  "[javascript]": {
+    "editor.defaultFormatter": "biomejs.biome"
+  },
+  "[javascriptreact]": {
+    "editor.defaultFormatter": "biomejs.biome"
+  },
+  "[typescript]": {
+    "editor.defaultFormatter": "biomejs.biome"
+  },
+  "[typescriptreact]": {
+    "editor.defaultFormatter": "biomejs.biome"
+  },
+  "[json]": {
+    "editor.defaultFormatter": "vscode.json-language-features"
+  },
+  "[jsonc]": {
+    "editor.defaultFormatter": "biomejs.biome"
+  }
+}

biome.json

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+{
+  "$schema": "https://biomejs.dev/schemas/2.3.6/schema.json",
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true
+  },
+  "files": {
+    "ignoreUnknown": false,
+    "includes": ["**", "!cloudflare-env.d.ts"]
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineWidth": 100
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true,
+      "a11y": {
+        "useButtonType": "warn"
+      },
+      "style": {
+        "noNonNullAssertion": "off",
+        "useImportType": "warn"
+      },
+      "suspicious": {
+        "noExplicitAny": "warn",
+        "noArrayIndexKey": "warn",
+        "noDocumentCookie": "warn",
+        "useIterableCallbackReturn": "warn"
+      },
+      "correctness": {
+        "useExhaustiveDependencies": "warn",
+        "noUnusedVariables": "warn"
+      }
+    }
+  },
+  "javascript": {
+    "formatter": {
+      "quoteStyle": "single",
+      "jsxQuoteStyle": "double",
+      "semicolons": "asNeeded",
+      "trailingCommas": "es5",
+      "arrowParentheses": "asNeeded"
+    }
+  },
+  "json": {
+    "formatter": {
+      "indentStyle": "space",
+      "indentWidth": 2
+    }
+  },
+  "css": {
+    "parser": {
+      "cssModules": false,
+      "tailwindDirectives": true
+    }
+  },
+  "assist": {
+    "enabled": true,
+    "actions": {
+      "source": {
+        "organizeImports": "on"
+      }
+    }
+  },
+  "overrides": [
+    {
+      "includes": ["**/*.mdx"],
+      "linter": {
+        "enabled": false
+      }
+    },
+    {
+      "includes": ["src/app/*/layout.tsx", "src/components/JsonLd.tsx"],
+      "linter": {
+        "rules": {
+          "security": {
+            "noDangerouslySetInnerHtml": "off"
+          }
+        }
+      }
+    }
+  ]
+}