feat: Sharp style, Tailwind+shadcn, dark navbar, nav restructure, Go/monorepo guidelines

Styling:
- Tailwind CSS v4 (preflight:false) integrated via PostCSS plugin
- shadcn/ui New York style with --radius:0 (sharp corners everywhere)
- Zero border-radius on ALL elements: buttons, code blocks, cards, admonitions, badges
- Navbar FORCE dark (#0a0a0a) in both light/dark modes via !important
- ThemeSynchronizer: bridges Docusaurus data-theme → shadcn .dark class
- Active sidebar item gets left border accent instead of rounded bg

React UI components (src/components/ui/index.tsx):
- Badge (6 variants: wip, stable, planned, success, warning, outline)
- Card + CardHeader + CardTitle + CardContent
- Callout (note/info/success/warning/danger) - sharp, left-border style
- PropertiesTable - monospace typed API reference tables
- StatusIndicator - operational/degraded/outage/maintenance

Navigation restructure:
- Introduction → Platform → Products → Engineering → Runbooks
- Old 'applications/' removed, moved to products/stock-market-pro/
- New Platform section: infrastructure overview + CI/CD pipeline docs
- New Engineering section: monorepo structure, Go stack, conventions
- New Runbooks section: incident severity, common procedures

Implementation guidelines (engineering/guidelines.md):
- Monorepo layout with go.work workspace
- Go as primary language (why + standard library table)
- Python as sidecar for data/ML workloads
- Code conventions: gofmt, error wrapping, logging, testing
- Git conventions: branch naming, conventional commits
- Makefile targets per app
- How to add a new application (step-by-step)

sidebars.ts

@@ -2,50 +2,75 @@ import type {SidebarsConfig} from '@docusaurus/plugin-content-docs';
 
 const sidebars: SidebarsConfig = {
   docsSidebar: [
+    /* ── Introduction ────────────────────────────────────── */
     {
       type: 'doc',
       id: 'intro/index',
-      label: '← Overview',
+      label: 'Introduction',
     },
+
+    /* ── Platform ────────────────────────────────────────── */
     {
       type: 'category',
-      label: 'Applications',
+      label: 'Platform',
+      collapsed: false,
+      items: [
+        'platform/overview',
+        'platform/cicd',
+      ],
+    },
+
+    /* ── Products ────────────────────────────────────────── */
+    {
+      type: 'category',
+      label: 'Products',
       collapsed: false,
       items: [
         {
           type: 'category',
-          label: '📈 Stock Market Pro',
-          link: { type: 'doc', id: 'applications/stock-market-professional/index' },
+          label: 'Stock Market Pro',
+          link: { type: 'doc', id: 'products/stock-market-pro/index' },
           items: [
             {
               type: 'category',
-              label: 'C4 Architecture',
-              collapsed: false,
+              label: 'Architecture (C4)',
               items: [
-                'applications/stock-market-professional/c4/context',
-                'applications/stock-market-professional/c4/containers',
-                'applications/stock-market-professional/c4/components',
+                'products/stock-market-pro/c4/context',
+                'products/stock-market-pro/c4/containers',
+                'products/stock-market-pro/c4/components',
               ],
             },
             {
               type: 'category',
               label: 'Modules',
               items: [
-                'applications/stock-market-professional/data-monitoring/index',
-                'applications/stock-market-professional/technical-analysis/index',
-                'applications/stock-market-professional/signal-generation/index',
+                'products/stock-market-pro/data-monitoring/index',
+                'products/stock-market-pro/technical-analysis/index',
+                'products/stock-market-pro/signal-generation/index',
               ],
             },
           ],
         },
       ],
     },
+
+    /* ── Engineering ─────────────────────────────────────── */
     {
       type: 'category',
-      label: 'Platform',
+      label: 'Engineering',
+      collapsed: false,
       items: [
-        'architecture/overview',
-        'guides/getting-started',
+        'engineering/guidelines',
+      ],
+    },
+
+    /* ── Runbooks ────────────────────────────────────────── */
+    {
+      type: 'category',
+      label: 'Runbooks',
+      collapsed: true,
+      items: [
+        'runbooks/index',
       ],
     },
   ],