feat: website analysis pipeline, voice agent, configurator improvements

- Site analysis: cheerio HTML parsing, inline tech stack detection (~20 CMS/framework/analytics signatures), Google PageSpeed API integration
- Gemini Live voice agent: WebSocket-based real-time voice mode with live transcript, selection chips, and mid-conversation website analysis
- Type/Talk mode toggle with silent capability detection
- Stepped progress animation during brief generation (4 animated steps)
- URL + thoughts fields in Step 2, phone + contact preference in Step 3
- AI prompt improvements: dedicated website analysis section, 30-min call, concrete benefits, industry depth
- Email redesign: branded templates with logo, proper markdown rendering for both client and admin
- French locale support for AI-generated briefs
- Smaller checkmark, compact booking CTA, expanded brief area

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.env.example

@@ -16,6 +16,9 @@ SMTP_PASS=your-smtp-password
 SMTP_FROM=hello@letsbe.biz
 ADMIN_EMAIL=hello@letsbe.biz
 
+# ── Gemini Live API (voice agent) ──
+GEMINI_API_KEY=your-gemini-api-key
+
 # ── Cal.com ──
 NEXT_PUBLIC_CALCOM_URL=https://cal.letsbe.biz