Add Guests module: API integration + passport identification

- Migration 009: add passport_series, passport_number, rating to guests table
- Backend route /api/hotels/:slug/guests: list, get (with history), create/upsert by passport, update, delete
- Frontend GuestsPage: loads from API, passport tab in modal, add guest form, search by passport
- api.ts: add guests API methods and GuestApiType

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

backend/migrations/009_guests.sql

@@ -0,0 +1,12 @@
+-- Migration 009 — Add passport_series, passport_number and rating to guests
+
+ALTER TABLE guests
+  ADD COLUMN IF NOT EXISTS passport_series VARCHAR(20),
+  ADD COLUMN IF NOT EXISTS passport_number VARCHAR(20),
+  ADD COLUMN IF NOT EXISTS rating          INTEGER NOT NULL DEFAULT 3
+    CHECK (rating BETWEEN 1 AND 5);
+
+-- Unique index: one profile per passport (series+number) per hotel
+CREATE UNIQUE INDEX IF NOT EXISTS idx_guests_passport_unique
+  ON guests(hotel_id, passport_series, passport_number)
+  WHERE passport_series IS NOT NULL AND passport_number IS NOT NULL;