feat(pitch-deck): English email templates, investor language preference, link-only invite mode

- Add English email template variants (greeting, message, closing, subject, CTA copy)
- Add `preferred_lang` column to `pitch_investors` — stored per investor, deck opens in that language by default
- Invite form: DE/EN language toggle that switches email defaults and pitch language setting
- Invite form: "Send email" toggle — when off, creates investor + returns magic link without sending email (for cold outreach attachment)
- `app/page.tsx`: initializes pitch language from investor's `preferred_lang` before first render (no flash)
- Migration 007 added to `/api/admin/migrate` route for production rollout

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

pitch-deck/lib/email-templates.ts

@@ -4,6 +4,19 @@ export const DEFAULT_MESSAGE =
 export const DEFAULT_CLOSING =
   'Gerne stehen wir Ihnen für einen persönlichen Austausch oder eine vertiefende Diskussion jederzeit zur Verfügung.\n\nMit freundlichen Grüßen,\nBenjamin Bönisch & Sharang Parnerkar\nGründer — BreakPilot'
 
-export function getDefaultGreeting(name: string | null): string {
+export const DEFAULT_GREETING_EN = 'Dear Sir or Madam'
+export const DEFAULT_MESSAGE_EN =
+  'we are delighted to grant you exclusive access to the interactive investor pitch deck of our planned venture <strong>BreakPilot</strong>.<br><br>BreakPilot addresses a core challenge facing modern software development: maintaining continuous regulatory compliance while sustaining high development velocity.<br><br>Our planned solution combines code security, automated compliance, and regulatory intelligence in an end-to-end platform. The goal is not only to surface deviations, but to actively guide organizations on how to operate their systems in maximum regulatory conformance and optimal performance — particularly in the context of AI systems and the EU AI Act.<br><br>The pitch deck provides a structured overview of the problem space, solution architecture, and our planned financing strategy.'
+export const DEFAULT_CLOSING_EN =
+  'We would be delighted to connect for a personal exchange or a deeper discussion at any time.\n\nBest regards,\nBenjamin Bönisch & Sharang Parnerkar\nFounders — BreakPilot'
+
+export function getDefaultGreeting(name: string | null, lang: 'de' | 'en' = 'de'): string {
+  if (lang === 'en') return name ? `Dear ${name}` : DEFAULT_GREETING_EN
   return name ? `Sehr geehrter Herr ${name}` : DEFAULT_GREETING
 }
+
+export function getDefaults(lang: 'de' | 'en') {
+  return lang === 'en'
+    ? { message: DEFAULT_MESSAGE_EN, closing: DEFAULT_CLOSING_EN }
+    : { message: DEFAULT_MESSAGE, closing: DEFAULT_CLOSING }
+}