feat: merge BetterCallClaude into Mitch - Swiss legal intelligence platform

- Add MCP HTTP client for 7 Swiss legal databases (BGE, entscheidsuche,
  fedlex, onlinekommentar, legal-citations, legal-persona, tas-jurisprudence)
- Integrate 9 MCP tools into chat tool loop (search_bge, search_swiss_decisions,
  verify_citation, search_federal_legislation, search_commentary,
  legal_strategy, legal_draft, legal_analyze)
- Replace generic system prompt with Swiss legal identity:
  Gutachtenstil reasoning, cantonal awareness, multi-language support (DE/FR/IT/EN),
  BGE/ATF/DTF citation standards
- Add Anwaltsgeheimnis privacy scanner (Art. 321 StGB / Art. 13 BGFA)
  blocking privileged content before external MCP calls
- Add 5 Swiss legal built-in workflows:
  litigation prep, contract review, due diligence, legal opinion, compliance check
- Rebrand frontend from Mike to Mitch across all user-facing surfaces
- Add Swiss quick-action buttons and Swiss Legal Intelligence badge
- Add COMPLIANCE.md with data residency and professional disclaimers
- Update README with Swiss capabilities and MCP integration docs