feat(dashboard): real business metrics with week-over-week trends

Dashboard KPIs were three flat counters with no trend data — the cards
rendered a neutral dash where the design intends movement indicators.
Summary now queries three trailing windows and emits four KPIs with
real deltas: bookings this week, completed (new CompletedCount metric
in both repositories), cancellations, and utilization in percentage
points. KPI labels localize in the frontend via a code-to-key map so
Czech operators no longer see English labels on live data.

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project.md

@@ -82,6 +82,14 @@
   - bookings surface the `waitlisted` status: stats card, filter option, warning-tone badge, demo seed entry; `dashboard.{status}` interpolation resolves the new i18n key automatically
   - `BookingRecord` now carries `created_at` (needed for fair waitlist ordering); `GetBookingByID` added to the repository surface
   - remaining: live staging validation; waitlist position display and manual promotion controls are not yet exposed
+- `[done/partial]` Milestone 12: Real dashboard business metrics
+  - `DashboardMetrics` gained `CompletedCount` (confirmed bookings already ended within the window) in both pgx and in-memory repositories
+  - `DashboardSummary` now queries three trailing windows (next 7d, last 7d, 7-14d ago) and emits four KPIs with real trend deltas: `bookings_this_week`, `completed`, `cancellations`, `utilization` (delta in percentage points)
+  - `DashboardKPI` carries optional `change`/`trend` (`up|down|neutral`); the KPI card already rendered these, so real data now drives the trend arrows instead of the previous `neutral`/`—` fallback
+  - KPI labels are localized in the frontend via a `code` → i18n-key map (`dashboard.kpi.bookingsThisWeek`, `cancellations`, `utilization`; `completed` reuses the existing key); backend labels stay English as a fallback
+  - the booking-trend chart was already bucketing real `allBookings` into the current week — confirmed, no change needed
+  - demo mode intentionally keeps curated static KPI values; real tenants get the computed set
+  - remaining: live staging validation; "new clients" KPI still has no backend metric (customer entity lacks first-booking tracking)
 
 ## Overview
 Bookra is a Czech-first booking SaaS for small local service businesses. It targets salons, massage therapists, small clinics, repair shops, and small studios/clubs that need a simple public booking flow, internal schedule management, reminders, and basic business reporting without becoming a full ERP.