feat(showcase): add PouchDB sample component and storage page

- Implemented PouchSample component for managing POS configurations and item inventories using PouchDB.
- Created StoragePage to encapsulate the PouchSample component.
- Added UI components page with various UI elements including buttons, forms, and data grids.
- Defined Electron type declarations for printing and auto-update functionalities.
- Extended event registry with custom application events for printing and stock updates.
- Configured Vite for the showcase application with React and Tailwind CSS support.
- Updated package.json and pnpm-lock.yaml to include necessary dependencies for the showcase app.

.devcontainer/devcontainer.json

@@ -18,7 +18,8 @@
   // 4173: VitePress Docs (Preview)
   // 5173: Web App (Must be strictly 5173 for Electron IPC compatibility)
   // 3000: Landing App (Isolated from Vite's default 517x blast radius)
-  "forwardPorts": [6060, 4173, 5173, 3000],
+  // 3005: Showcase App
+  "forwardPorts": [6060, 4173, 5173, 3000, 3005],
   
   "portsAttributes": {
     "6060": {
@@ -33,6 +34,10 @@
       "label": "Web App (Electron Target)",
       "onAutoForward": "notify"
     },
+    "3005": {
+      "label": "Showcase App",
+      "onAutoForward": "notify"
+    },
     "3000": {
       "label": "Landing App (Public)",
       "onAutoForward": "notify"