feat: Modern styling, draw.io integration, and C4 architecture docs

Styling:
- Dark-first design (Vercel/Linear inspired) with Geist font
- Custom CSS with full --ifm- token overrides
- Glassmorphic navbar, refined sidebar, modern tables
- Gradient hero with animated glow, app cards, C4 section
- Custom badge, tag, and callout components
- Announcement bar, TOC config, dark scrollbar

draw.io:
- Added docusaurus-plugin-drawio + raw-loader
- SMP full pipeline diagram (smp-pipeline.drawio)
- Embedded in architecture overview

Mermaid:
- Added @docusaurus/theme-mermaid
- C4Context, C4Container, C4Component diagrams
- Sequence and graph diagrams in architecture

C4 Architecture (Stock Market Professional):
- L1 Context: system in the world, actors, external systems
- L2 Containers: Data Ingestor, Analysis Engine, Signal Generator, TimescaleDB, Notifier
- L3 Components: deep component breakdown with mermaid C4Component diagrams

Other:
- Sidebar restructured with C4 section and Modules section
- Homepage rebuilt as modern dark landing page

docs/architecture/overview.md

@@ -6,47 +6,67 @@ sidebar_position: 1
 
 ## Overview
 
-All SKIC Playground applications share a common infrastructure pattern:
+All SKIC Playground applications share a common infrastructure built on TrueNAS SCALE and Gitea.
 
-```
-┌─────────────────────────────────────────────────────┐
-│                   TrueNAS SCALE                      │
-│                                                      │
-│  ┌──────────┐  ┌──────────┐  ┌──────────────────┐  │
-│  │  Gitea   │  │ Registry │  │  App Containers  │  │
-│  │  + CI/CD │  │  (Zot)   │  │                  │  │
-│  └──────────┘  └──────────┘  └──────────────────┘  │
-│                                                      │
-│  ┌──────────┐  ┌──────────┐  ┌──────────────────┐  │
-│  │Keycloak  │  │  Hermes  │  │   Monitoring     │  │
-│  │  (Auth)  │  │  (Agent) │  │                  │  │
-│  └──────────┘  └──────────┘  └──────────────────┘  │
-└─────────────────────────────────────────────────────┘
+## Full Pipeline — Interactive Diagram
+
+import Drawio from '@theme/Drawio';
+import smpPipeline from '!!raw-loader!./diagrams/smp-pipeline.drawio';
+
+<Drawio content={smpPipeline} />
+
+## Infrastructure
+
+```mermaid
+graph TB
+    subgraph TrueNAS["🖥 TrueNAS SCALE — lego-cloud.eu"]
+        Gitea["🗂 Gitea\nSource + CI/CD"]
+        Zot["📦 Zot Registry\n:30264"]
+        Apps["🐳 App Containers"]
+        Hermes["🤖 Hermes Agent\nAI Operations"]
+        Keycloak["🔐 Keycloak\nAuth / SSO"]
+    end
+
+    Gitea -->|push image| Zot
+    Zot -->|pull & deploy| Apps
+    Hermes -->|automates| Gitea
+    Hermes -->|manages| Apps
+    Keycloak -->|secures| Apps
 ```
 
 ## Shared Services
 
 | Service | URL | Purpose |
 |---|---|---|
-| Gitea | gitea.lego-cloud.eu | Source code, CI/CD |
-| Keycloak | keycloak.lego-cloud.eu | Authentication, SSO |
-| Zot Registry | :30264 | Container images |
-| Hermes Agent | Local | AI operations, automation |
+| Gitea | gitea.lego-cloud.eu | Source code, CI/CD, issue tracking |
+| Keycloak | keycloak.lego-cloud.eu | Authentication & SSO |
+| Zot Registry | :30264 | OCI container image registry |
+| Hermes Agent | Local | AI operations, automation, documentation |
 
-## CI/CD Pattern
+## CI/CD Flow
 
-All applications follow the same Gitea Actions workflow:
+```mermaid
+sequenceDiagram
+    participant Dev as Developer / Jarvis
+    participant Git as Gitea
+    participant CI as Gitea Actions
+    participant Reg as Zot Registry
+    participant Host as TrueNAS
 
-1. **Push to main** → Build + Test
-2. **Build container** → Push to Zot registry
-3. **Deploy** → Update running container
-4. **Docs update** → Rebuild documentation site
+    Dev->>Git: git push main
+    Git->>CI: Trigger workflow
+    CI->>CI: pnpm install
+    CI->>CI: pnpm build
+    CI->>Reg: docker push image
+    CI->>Host: Deploy updated container
+    Host-->>Dev: ✅ Live
+```
 
 ## Repository Structure
 
 ```
 skic-v1-playground/
-├── documentation/          # This docs site
-├── stock-market-pro/       # (Planned) Trading system
-└── ...                     # Future applications
+├── documentation/          ← This docs site (Docusaurus)
+├── stock-market-pro/       ← (Planned) Trading system
+└── ...                     ← Future applications
 ```