Add scenario-modeler-server example

Demo MCP App for SaaS financial planning with:
- Interactive sliders for MRR, growth, churn, margin, and costs
- 12-month projection charts (MRR, Gross Profit, Net Profit)
- 5 pre-built scenario templates (Bootstrapped, VC Rocketship, etc.)
- Template comparison overlay for strategy analysis
- Light/dark theme support

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

examples/scenario-modeler-server/src/hooks/useTheme.ts

@@ -0,0 +1,25 @@
+import { useState, useEffect } from "react";
+
+export type Theme = "light" | "dark";
+
+export function useTheme(): Theme {
+  const [theme, setTheme] = useState<Theme>(() => {
+    if (typeof window === "undefined") return "light";
+    return window.matchMedia("(prefers-color-scheme: dark)").matches
+      ? "dark"
+      : "light";
+  });
+
+  useEffect(() => {
+    const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
+
+    const handleChange = (e: MediaQueryListEvent) => {
+      setTheme(e.matches ? "dark" : "light");
+    };
+
+    mediaQuery.addEventListener("change", handleChange);
+    return () => mediaQuery.removeEventListener("change", handleChange);
+  }, []);
+
+  return theme;
+}