feat: Initial Docusaurus setup with Stock Market Professional docs

- Set up Docusaurus with pnpm and TypeScript
- Structured docs for multi-application portfolio
- Added Stock Market Professional documentation:
  - Architecture & system design
  - Data monitoring module
  - Technical analysis engine
  - Signal generation with constraints (max 3/day, 30min hold)
- Added platform architecture overview
- Added getting started guide
- Added Gitea Actions CI/CD pipeline (build + artifact)

sidebars.ts

@@ -0,0 +1,43 @@
+import type {SidebarsConfig} from '@docusaurus/plugin-content-docs';
+
+const sidebars: SidebarsConfig = {
+  docsSidebar: [
+    'intro/index',
+    {
+      type: 'category',
+      label: 'Applications',
+      items: [
+        {
+          type: 'category',
+          label: 'Stock Market Professional',
+          link: {
+            type: 'doc',
+            id: 'applications/stock-market-professional/index',
+          },
+          items: [
+            'applications/stock-market-professional/overview/architecture',
+            'applications/stock-market-professional/data-monitoring/index',
+            'applications/stock-market-professional/technical-analysis/index',
+            'applications/stock-market-professional/signal-generation/index',
+          ],
+        },
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Architecture',
+      items: [
+        'architecture/overview',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Guides',
+      items: [
+        'guides/getting-started',
+      ],
+    },
+  ],
+};
+
+export default sidebars;