feat(kanban): reporte diario al click en dia del calendario (issue 0093)

Adds a daily report dashboard accessible by clicking a day number in the
calendar view. Renders inside a full-width modal (90% width).

Backend (new file backend/reports.go):
- Type DailyReport with KPIs, rankings, done_cards list, reopened cards,
  3-bucket stale list (7/14/30d), lead time avg+p50+p95, 24-hour
  movement histogram, deadlines met/missed list, tag distribution and
  archived count.
- DB.DailyReportFor(date, tz) uses Europe/Madrid by default; computes
  [start,end) in local time, converts to UTC and queries:
  * cards.completed_at in range  -> done list
  * card_events kind=created in range -> created counts
  * card_column_history.entered_at in range -> moves + hourly
  * previousColumnWasDone() -> reopened detection
  * card_lock_history overlapping the day -> blocked_ms
  * stale buckets: open history entries on non-done columns aged >=7d
- New route GET /api/reports/daily?date=YYYY-MM-DD&tz=Europe/Madrid.

Frontend:
- api.ts: DailyReport type + dailyReport(date, tz?) call.
- New component DailyReportView (components/DailyReport.tsx):
  * 6 KPI cards (Hechas, Creadas, Movimientos, Bloqueado, Reabiertas,
    Deadlines on-time %).
  * 4 ranking cards (Top assignees done, Top assignees created,
    Top requesters atendidas, Top requesters aportadas).
  * Done cards table with click-to-jump (links open the card in board).
  * Mantine BarChart with movements per hour.
  * Tag chips, reopened list, deadlines list with late_ms, stale buckets.
- CalendarView wraps the day number in UnstyledButton with data-test
  attribute and forwards onOpenDailyReport.
- App.handleOpenDailyReport opens modals.open size 90% with the view;
  click on a card title closes the modal and jumps to the board with
  highlight (reuses existing handleJumpToCard).

Tests (e2e/daily-report.spec.ts):
- Endpoint shape: kpis, done_cards, hourly_moves[24], stale buckets.
- Calendar day click opens the modal with "Reporte diario" title and
  KPI labels visible.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/handlers.go

@@ -437,6 +437,26 @@ func handleRestoreCard(db *DB) http.HandlerFunc {
 	}
 }
 
+// GET /api/reports/daily?date=YYYY-MM-DD&tz=Europe/Madrid
+func handleDailyReport(db *DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		date := r.URL.Query().Get("date")
+		if date == "" {
+			date = time.Now().UTC().Format("2006-01-02")
+		}
+		tz := r.URL.Query().Get("tz")
+		if tz == "" {
+			tz = "Europe/Madrid"
+		}
+		rep, err := db.DailyReportFor(date, tz)
+		if err != nil {
+			badRequest(w, err.Error())
+			return
+		}
+		infra.HTTPJSONResponse(w, http.StatusOK, rep)
+	}
+}
+
 // GET /api/archive
 func handleListArchive(db *DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -511,6 +531,7 @@ func apiRoutes(db *DB, chatWorkdir string, logger *ChatLogger, internalToken str
 		{Method: "GET", Path: "/api/cards/{id}/history", Handler: handleCardHistory(db)},
 		{Method: "GET", Path: "/api/trash", Handler: handleListTrash(db)},
 		{Method: "POST", Path: "/api/cards/{id}/restore", Handler: handleRestoreCard(db)},
+		{Method: "GET", Path: "/api/reports/daily", Handler: handleDailyReport(db)},
 		{Method: "GET", Path: "/api/archive", Handler: handleListArchive(db)},
 		{Method: "POST", Path: "/api/cards/{id}/archive", Handler: handleArchiveCard(db)},
 		{Method: "POST", Path: "/api/cards/{id}/unarchive", Handler: handleUnarchiveCard(db)},