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)

docs/platform/cicd.md

@@ -0,0 +1,65 @@
+---
+sidebar_position: 2
+---
+
+# CI/CD Pipeline
+
+All applications follow a single, consistent Gitea Actions pipeline.
+
+## Flow
+
+```mermaid
+sequenceDiagram
+    participant J as Jarvis / Dev
+    participant G as Gitea
+    participant A as Actions Worker
+    participant R as Zot Registry
+    participant H as TrueNAS Host
+
+    J->>G: git push main
+    G->>A: Trigger workflow
+    A->>A: pnpm/go build + test
+    A->>R: docker push image
+    A->>H: Deploy (restart container)
+    H-->>J: ✅ Live
+```
+
+## Workflow Template
+
+```yaml
+# .gitea/workflows/build.yml
+name: Build and Deploy
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build
+        run: make build    # or go build / pnpm build
+
+      - name: Test
+        run: make test
+
+      - name: Docker build & push
+        if: github.ref == 'refs/heads/main'
+        run: |
+          docker build -t $ZOT_REGISTRY/$APP_NAME:$GITHUB_SHA .
+          docker push $ZOT_REGISTRY/$APP_NAME:$GITHUB_SHA
+
+      - name: Deploy
+        if: github.ref == 'refs/heads/main'
+        run: |
+          ssh deploy@lego-cloud.eu "docker pull && docker restart $APP_NAME"
+```
+
+## Gitea Actions Runners
+
+Runners need to be registered on the Gitea instance. See [Gitea Actions documentation](https://docs.gitea.com/usage/actions/quickstart) for setup.