feat(pitch): showcase mode — per-investor toggle hides financial/investor slides for customer demos

Adds is_showcase boolean to pitch_investors; when set, filters out financials,
the ask, cap table, assumptions, finanzplan, risks, and intro-presenter slides.
Slide navigation is fully dynamic — progress bar and counts update accordingly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pitch-deck/app/api/auth/me/route.ts

@@ -14,7 +14,7 @@ export async function GET() {
   }
 
   const { rows } = await pool.query(
-    `SELECT id, email, name, company, status, last_login_at, login_count, created_at
+    `SELECT id, email, name, company, status, last_login_at, login_count, created_at, is_showcase
      FROM pitch_investors WHERE id = $1`,
     [session.sub]
   )