feat: implement file editor with syntax highlighting and editing

- Install react-simple-code-editor and prismjs dependencies
- Create language detection utility with 50+ file extensions
- Create SyntaxHighlighter component with Prism.js highlighting
- Create CodeEditor component with syntax-highlighted editing
- Create CommitDialog with diff preview and commit message
- Create FileEditor component integrating view/edit/commit flow
- Replace FileViewer with FileEditor in RepoWorkspace
- Add comprehensive CSS styles for editor, highlighter, and dialog
- Support keyboard shortcuts: Ctrl+E (toggle edit), Ctrl+S (save)
- Quality gates: typecheck ✓ lint ✓ build ✓

apps/web/package-lock.json

@@ -8,10 +8,13 @@
       "name": "headquarter-web",
       "version": "0.1.0",
       "dependencies": {
+        "@types/prismjs": "^1.26.6",
         "axios": "^1.6.0",
+        "prismjs": "^1.30.0",
         "react": "^18.2.0",
         "react-dom": "^18.2.0",
         "react-router-dom": "^6.20.0",
+        "react-simple-code-editor": "^0.14.1",
         "tailwindcss": "^3.3.0"
       },
       "devDependencies": {
@@ -2127,6 +2130,12 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/prismjs": {
+      "version": "1.26.6",
+      "resolved": "https://registry.npmjs.org/@types/prismjs/-/prismjs-1.26.6.tgz",
+      "integrity": "sha512-vqlvI7qlMvcCBbVe0AKAb4f97//Hy0EBTaiW8AalRnG/xAN5zOiWWyrNqNXeq8+KAuvRewjCVY1+IPxk4RdNYw==",
+      "license": "MIT"
+    },
     "node_modules/@types/prop-types": {
       "version": "15.7.15",
       "resolved": "https://registry.npmjs.org/@types/prop-types/-/prop-types-15.7.15.tgz",
@@ -5091,6 +5100,15 @@
         "url": "https://github.com/chalk/ansi-styles?sponsor=1"
       }
     },
+    "node_modules/prismjs": {
+      "version": "1.30.0",
+      "resolved": "https://registry.npmjs.org/prismjs/-/prismjs-1.30.0.tgz",
+      "integrity": "sha512-DEvV2ZF2r2/63V+tK8hQvrR2ZGn10srHbXviTlcv7Kpzw8jWiNTqbVgjO3IY8RxrrOUF8VPMQQFysYYYv0YZxw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/proxy-from-env": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/proxy-from-env/-/proxy-from-env-2.1.0.tgz",
@@ -5205,6 +5223,16 @@
         "react-dom": ">=16.8"
       }
     },
+    "node_modules/react-simple-code-editor": {
+      "version": "0.14.1",
+      "resolved": "https://registry.npmjs.org/react-simple-code-editor/-/react-simple-code-editor-0.14.1.tgz",
+      "integrity": "sha512-BR5DtNRy+AswWJECyA17qhUDvrrCZ6zXOCfkQY5zSmb96BVUbpVAv03WpcjcwtCwiLbIANx3gebHOcXYn1EHow==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": ">=16.8.0",
+        "react-dom": ">=16.8.0"
+      }
+    },
     "node_modules/read-cache": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/read-cache/-/read-cache-1.0.0.tgz",