feat(pitch-deck): branded short links for magic URLs (pitch.breakpilot.ai/p/ab3xk2)

- New pitch_short_links table stores 6-char alphanumeric codes mapped to magic link tokens
- GET /p/[code] redirects to /auth/verify?token=... (302, validates expiry)
- All magic link generation points (invite, generate-link, resend) now create a short code
- Emails (invite + resend) use the short URL — less token-like, cleaner for spam filters
- Copy-link UI shows short URL prominently with full URL as fallback
- Migration 008 added to /api/admin/migrate

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

pitch-deck/app/p/[code]/route.ts

@@ -0,0 +1,21 @@
+import { NextRequest, NextResponse } from 'next/server'
+import pool from '@/lib/db'
+
+interface Ctx { params: Promise<{ code: string }> }
+
+export async function GET(request: NextRequest, ctx: Ctx) {
+  const { code } = await ctx.params
+
+  const { rows } = await pool.query(
+    `SELECT sl.token FROM pitch_short_links sl
+     JOIN pitch_magic_links ml ON ml.token = sl.token
+     WHERE sl.short_code = $1 AND ml.expires_at > NOW()`,
+    [code.toLowerCase()],
+  )
+
+  if (rows.length === 0) {
+    return NextResponse.redirect(new URL('/auth?error=invalid', request.url))
+  }
+
+  return NextResponse.redirect(new URL(`/auth/verify?token=${rows[0].token}`, request.url))
+}