Fayrouz Improvements

PaidBy field in expense logging is case-sensitive and causes broken balances when multiple users log expenses with different name formats (e.g. "giulia", "Giulia", "giuliatomas" all treated as separate payers). Fix needed: - Normalize PaidBy to lowercase or canonical username on write - OR match case-insensitively when reading/calculating balances - Map common aliases to canonical account (e.g. giulia, Giulia, giuliatomas → @giuliatomas) Context: Discovered during Uzbekistan trip when Youssef and Giulia were both logging expenses independently. --- Calendar fixes needed: - Calendar events still have issues that need resolving (editing, display, sync) - Need ability to edit and delete existing entries/transactions (pantry entries or any logged item) - Currently no way to correct wrong entries after the fact — must be able to change or delete any logged record --- Group expense experience needs to be more robust and smart: - Fayrouz on Giulia's side was hallucinating — not actually logging expenses, not calculating fields correctly, only throwing back numbers without writing anything - Root cause: anti-hallucination rules and verified-state enforcement must apply equally to ALL users in a group, not just the admin - Fix needed: - Every group expense write MUST return verified_state before confirming to user - Never say "logged" or "saved" unless the tool returned success - Auto-calculate splits correctly on write, not just display - Group members must have same trust level as admin for expense logging accuracy - Never break the trust — shared money is serious