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/applications/stock-market-professional/c4/context.md

@@ -0,0 +1,50 @@
+---
+sidebar_position: 1
+---
+
+# L1 — System Context
+
+> **C4 Level 1**: Shows how Stock Market Professional fits into the world — who uses it, and what external systems it depends on.
+
+:::info C4 Model — Level 1
+The Context diagram answers: *What does this system do, and who / what interacts with it?*
+:::
+
+## Context Diagram
+
+```mermaid
+C4Context
+    title System Context — Stock Market Professional
+
+    Person(trader, "Trader (Lego)", "Human operator who reviews signals and executes trades manually.")
+
+    System(smp, "Stock Market Professional", "Monitors markets, runs technical analysis, and emits daily trading signals.")
+
+    System_Ext(marketData, "Market Data Provider", "Real-time & historical price feeds (Yahoo Finance, Alpha Vantage, Polygon.io)")
+    System_Ext(discord, "Discord", "Signal delivery channel — daily trading plans posted to a server.")
+    System_Ext(broker, "Broker / Trading Platform", "Where the trader manually executes trades (e.g. Interactive Brokers, MetaTrader).")
+    System_Ext(newsApi, "Economic Calendar / News API", "High-impact event feed used to filter signals around news releases.")
+
+    Rel(trader, smp, "Reviews signals and trading plan")
+    Rel(smp, marketData, "Fetches OHLCV data", "REST / WebSocket")
+    Rel(smp, discord, "Posts daily plan & alerts", "Webhook / Bot API")
+    Rel(smp, newsApi, "Queries upcoming events", "REST API")
+    Rel(trader, broker, "Executes trades manually", "Web UI / API")
+```
+
+## Actors & Systems
+
+| Entity | Type | Role |
+|---|---|---|
+| Trader (Lego) | Person | Reviews daily signal plan, executes trades manually |
+| Market Data Provider | External System | Source of truth for price data |
+| Discord | External System | Primary delivery channel for signals |
+| Broker / Trading Platform | External System | Where actual trades happen (out of scope) |
+| Economic Calendar API | External System | News filter to avoid high-impact event windows |
+
+## Key Constraints
+
+- **No auto-trading** — all order execution is manual
+- **Signal limit** — max **3 signals per day** to enforce quality
+- **Hold time** — max **30 minutes** per position (scalping / intraday)
+- **Manual review** — trader has final say on all entries