Refactor: ES module architecture, tauri-plugin-store, unified design

Major changes:
- ES module system: main.js as central hub, shared modules
- tauri-plugin-store for persistent storage (dialog, fs plugins added)
- tauri-plugin-dialog for folder selection
- tauri-plugin-fs for real file system scanning
- Removed MOCK_FILES/FILE_TREE - real file scanner implemented
- All pages use unified page-header + page-content layout
- Custom titlebar with window controls
- Onboarding: 4-step flow with folder selection (Downloads default)
- CSS: unified design system, .hidden utility class added
- SVG icons throughout (no emoji)

Note: onboarding.js downloadDir() has runtime issue - needs fix

package-lock.json

@@ -8,8 +8,13 @@
       "name": "chakmate",
       "version": "1.0.0",
       "dependencies": {
+        "@fontsource/noto-color-emoji": "^5.2.12",
         "@fontsource/noto-sans-kr": "^5.2.9",
-        "@fontsource/outfit": "^5.2.8"
+        "@fontsource/outfit": "^5.2.8",
+        "@tauri-apps/api": "^2.11.0",
+        "@tauri-apps/plugin-dialog": "^2.7.1",
+        "@tauri-apps/plugin-fs": "^2.5.1",
+        "@tauri-apps/plugin-store": "^2.4.3"
       },
       "devDependencies": {
         "@tauri-apps/cli": "^2.0.0",
@@ -399,6 +404,14 @@
         "node": ">=12"
       }
     },
+    "node_modules/@fontsource/noto-color-emoji": {
+      "version": "5.2.12",
+      "resolved": "https://registry.npmjs.org/@fontsource/noto-color-emoji/-/noto-color-emoji-5.2.12.tgz",
+      "integrity": "sha512-UVOh4qxD/y42mcB4XvEdpV1WE01zn7O4+4tAWwzp5QAd4JY5jWPHu3/3T1kQoD04oYbQ5cJ9SI12IfcCKaS8aw==",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
     "node_modules/@fontsource/noto-sans-kr": {
       "version": "5.2.9",
       "resolved": "https://registry.npmjs.org/@fontsource/noto-sans-kr/-/noto-sans-kr-5.2.9.tgz",
@@ -810,6 +823,15 @@
         "win32"
       ]
     },
+    "node_modules/@tauri-apps/api": {
+      "version": "2.11.0",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/api/-/api-2.11.0.tgz",
+      "integrity": "sha512-7CinYODhky9lmO23xHnUFv0Xt43fbtWMyxZcLcRBlFkcgXKuEirBvHpmtJ89YMhyeGcq20Wuc47Fa4XjyniywA==",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/tauri"
+      }
+    },
     "node_modules/@tauri-apps/cli": {
       "version": "2.11.2",
       "resolved": "https://registry.npmjs.org/@tauri-apps/cli/-/cli-2.11.2.tgz",
@@ -1015,6 +1037,30 @@
         "node": ">= 10"
       }
     },
+    "node_modules/@tauri-apps/plugin-dialog": {
+      "version": "2.7.1",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/plugin-dialog/-/plugin-dialog-2.7.1.tgz",
+      "integrity": "sha512-OK1UBXYt+ojcmxMktzzuyonYIFta8CmAASpX+CA+DTGK24KlHjhYI6x2iOJ/TjZF4N7/ACK1oFmEOjIY9IhzOQ==",
+      "dependencies": {
+        "@tauri-apps/api": "^2.11.0"
+      }
+    },
+    "node_modules/@tauri-apps/plugin-fs": {
+      "version": "2.5.1",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/plugin-fs/-/plugin-fs-2.5.1.tgz",
+      "integrity": "sha512-9Lz+Jopp6QyeEWhlpkMx4R/+P9HgR+AVAI4vOZhlT8Xaymtz8iVI/Ov984/XTqgJz/5gz5NretqPB/XEMS3NhQ==",
+      "dependencies": {
+        "@tauri-apps/api": "^2.11.0"
+      }
+    },
+    "node_modules/@tauri-apps/plugin-store": {
+      "version": "2.4.3",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/plugin-store/-/plugin-store-2.4.3.tgz",
+      "integrity": "sha512-9LWPj9yMphRi9czEtUv87XHbl1b6xgd9EXpPrUnq6nG7+nbtoF84d4Kwz9xhAv/Hf30sr58pq7EOlyI936y8qw==",
+      "dependencies": {
+        "@tauri-apps/api": "^2.11.0"
+      }
+    },
     "node_modules/@types/estree": {
       "version": "1.0.8",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.8.tgz",