Show the next 30 nights on a calendar #110

Blocked by: #107

Problem

The calendar is the manager's main screen: they review the month at a glance and spot which nights moved. Today it's a static prototype with placeholder prices.

Goal

A month calendar showing the recommended rate for each night, how it changed since the last update, and the events driving it, loaded in one call.

Scope

• A month view (Monday to Sunday) with previous, next and "this month" controls.
• Each night's card:
  • the date and the rate in €;
  • the change since the last update (e.g. ↑ €10, ↓ €10), hidden when there's none;
  • the biggest event's name;
  • the manager's own rate when they've set one, marked so it's clear it's theirs;
  • a demand colour.
• Load the range in one call to the recommendations route with days.
• Clicking a night opens a popover with a short summary and an "Open day" link to the night detail page.
• Past nights are shown greyed but still open, so feedback can be given after the night.
• Empty state when the hotel has no trained model yet.

Design

• Follow the existing calendar design, with these changes:
  • leave out "Comp set median" and "Comp set gap" (no competitor data);
  • mark the manager's own rate on a card;
  • show "% sold" and "Pickup, 7 days" only if the API provides them; otherwise leave them out.
• Open question: which "Color by" options to keep (demand, occupancy, price change, events, weather) and what each colour means.
• Open question: the design says "Rates shown are Double, lowest available"; with one room type, what should this label say?

Acceptance criteria

• The design changes are agreed before building.
• The calendar shows 30+ nights from one API call (mocked until the backend is ready), with no placeholder numbers.
• Each card shows its rate, change and top event as described.
• Nights with a manager's rate show it, marked as theirs.
• Clicking a night opens the popover; "Open day" opens the night detail page.
• Without a trained model, the calendar shows a clear message instead of an error.