feat(kanban): bocadillo agente + PDF descargable en reporte diario (issue 0094)

Anade tres capas sobre el reporte diario del issue 0093:

1) Bocadillo del agente: cuadro azul encima de "Tareas hechas" con un
   resumen en lenguaje natural (max 4 frases) generado por claude -p
   sobre el JSON del reporte. Botones Regenerar e icono Settings.

2) Settings del prompt: modal con textarea editable para el template
   del agente (key=daily_report_prompt). Compartido por todos los
   usuarios. Boton Restablecer por defecto.

3) PDF descargable: boton que abre ventana nueva con HTML imprimible
   (estilo A4, KPIs filtrados, tabla con enlaces absolutos por card).
   Permite compartir el listado de tareas hechas con los solicitantes.

Backend:
- Migration 013 anade tablas daily_summaries y settings; seed del
  prompt por defecto en castellano.
- daily_summary.go con GetSetting/SetSetting, GetDailySummary/Upsert,
  runClaudePrompt (envuelve claude -p) y GenerateDailySummary que
  orquesta DailyReportFor + plantilla + claude + persist.
- Nuevos endpoints:
  * GET  /api/reports/daily/summary
  * POST /api/reports/daily/summary
  * GET  /api/settings/{key}
  * PUT  /api/settings/{key}

Frontend:
- api.ts: getDailySummary, generateDailySummary, getSetting, setSetting.
- DailyReport.tsx: estado de summary, settingsOpen, promptDraft,
  filterRequester, filterAssignee, filteredDoneCards, exportPDF.
- Bocadillo con IconSparkles + IconRefresh + IconSettings.
- Modal de prompt con Guardar/Cancelar/Reset.
- Filtros Select por solicitante y asignado encima de la tabla.
- exportPDF abre window.open con HTML self-contained que incluye
  enlaces ${origin}/?card=${id} y window.print() automatico.

E2E nuevo (daily-summary-pdf.spec.ts): CRUD del setting, GET summary
shape, presencia del boton PDF/Settings/Regenerar en el modal. No
invoca claude real (binario externo, no disponible en CI).

Suite completa 11/11 pasa.

backend/daily_summary.go

@@ -0,0 +1,143 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// DailySummary persisted row.
+type DailySummary struct {
+	Date        string  `json:"date"`
+	Summary     string  `json:"summary"`
+	Prompt      string  `json:"prompt"`
+	Model       string  `json:"model"`
+	GeneratedAt string  `json:"generated_at"`
+	GeneratedBy *string `json:"generated_by"`
+}
+
+func (db *DB) GetDailySummary(date string) (*DailySummary, error) {
+	row := db.conn.QueryRow(`SELECT date, summary, prompt, model, generated_at, generated_by FROM daily_summaries WHERE date=?`, date)
+	var s DailySummary
+	var by sql.NullString
+	if err := row.Scan(&s.Date, &s.Summary, &s.Prompt, &s.Model, &s.GeneratedAt, &by); err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		return nil, err
+	}
+	if by.Valid {
+		v := by.String
+		s.GeneratedBy = &v
+	}
+	return &s, nil
+}
+
+func (db *DB) UpsertDailySummary(s DailySummary) error {
+	var by any = nil
+	if s.GeneratedBy != nil {
+		by = *s.GeneratedBy
+	}
+	_, err := db.conn.Exec(`
+		INSERT INTO daily_summaries (date, summary, prompt, model, generated_at, generated_by)
+		VALUES (?,?,?,?,?,?)
+		ON CONFLICT(date) DO UPDATE SET
+		  summary=excluded.summary,
+		  prompt=excluded.prompt,
+		  model=excluded.model,
+		  generated_at=excluded.generated_at,
+		  generated_by=excluded.generated_by
+	`, s.Date, s.Summary, s.Prompt, s.Model, s.GeneratedAt, by)
+	return err
+}
+
+func (db *DB) GetSetting(key string) (string, error) {
+	var v string
+	err := db.conn.QueryRow(`SELECT value FROM settings WHERE key=?`, key).Scan(&v)
+	if err == sql.ErrNoRows {
+		return "", nil
+	}
+	return v, err
+}
+
+func (db *DB) SetSetting(key, value string, by *string) error {
+	now := nowRFC3339()
+	var byArg any = nil
+	if by != nil {
+		byArg = *by
+	}
+	_, err := db.conn.Exec(`
+		INSERT INTO settings (key, value, updated_at, updated_by) VALUES (?,?,?,?)
+		ON CONFLICT(key) DO UPDATE SET value=excluded.value, updated_at=excluded.updated_at, updated_by=excluded.updated_by
+	`, key, value, now, byArg)
+	return err
+}
+
+// runClaudePrompt executes `claude -p` with the given user prompt; returns
+// stdout trimmed. Times out via claudeTimeout from chat.go.
+func runClaudePrompt(ctx context.Context, prompt string) (string, error) {
+	ctx, cancel := context.WithTimeout(ctx, claudeTimeout)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, claudeBinary(), "-p", "--model", claudeModel())
+	cmd.Stdin = strings.NewReader(prompt)
+	var out, errb bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = &errb
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("claude -p failed: %v: %s", err, strings.TrimSpace(errb.String()))
+	}
+	return strings.TrimSpace(out.String()), nil
+}
+
+// BuildDailySummaryPrompt composes the prompt for the LLM by interpolating the
+// configurable instruction template with the JSON of the report.
+func BuildDailySummaryPrompt(template string, report *DailyReport) (string, error) {
+	js, err := json.MarshalIndent(report, "", "  ")
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s\n\n<reporte_json>\n%s\n</reporte_json>\n", template, string(js)), nil
+}
+
+// GenerateDailySummary builds the prompt, calls Claude, persists and returns
+// the resulting summary. actorID is optional (empty = anon/system).
+func (db *DB) GenerateDailySummary(ctx context.Context, date, tz, actorID string) (*DailySummary, error) {
+	rep, err := db.DailyReportFor(date, tz)
+	if err != nil {
+		return nil, err
+	}
+	tmpl, err := db.GetSetting("daily_report_prompt")
+	if err != nil {
+		return nil, err
+	}
+	if tmpl == "" {
+		tmpl = "Resume el reporte diario en 4 frases cortas, en castellano, sin inventar datos."
+	}
+	prompt, err := BuildDailySummaryPrompt(tmpl, rep)
+	if err != nil {
+		return nil, err
+	}
+	summary, err := runClaudePrompt(ctx, prompt)
+	if err != nil {
+		return nil, err
+	}
+	rec := DailySummary{
+		Date:        date,
+		Summary:     summary,
+		Prompt:      tmpl,
+		Model:       claudeModel(),
+		GeneratedAt: time.Now().UTC().Format(time.RFC3339Nano),
+	}
+	if actorID != "" {
+		rec.GeneratedBy = &actorID
+	}
+	if err := db.UpsertDailySummary(rec); err != nil {
+		return nil, err
+	}
+	return &rec, nil
+}