maven: calendar event querying (task 3)

Store: CalendarEvents(ctx, from, to) — filters caldav facts by key date prefix.
IPC: full wiring through interface, server dispatch, and client.
Router: ParseCalendarDate (сегодня/завтра), CalendarEventFormatter (RU reply).
Voice: calendar detection before notes RAG in IntentQuery handler.
Tests: store integration test, date parser tests, formatter tests.

Co-Authored-By: opencode <opencode@anthropic.com>

internal/ipc/api.go

@@ -123,6 +123,10 @@ type outcomesReq struct {
 type nReq struct {
 	N int `json:"n"`
 }
+type calendarEventsReq struct {
+	From time.Time `json:"from"`
+	To   time.Time `json:"to"`
+}
 type revertReq struct {
 	Key string `json:"key"`
 }
@@ -221,6 +225,7 @@ type CoreAPI interface {
 	ResolveNudge(ctx context.Context, id int64, outcome string, ts time.Time) error
 	RecentOutcomes(ctx context.Context, rule string, n int) ([]string, error)
 	RecentFacts(ctx context.Context, n int) ([]Fact, error)
+	CalendarEvents(ctx context.Context, from, to time.Time) ([]Fact, error)
 	RecentNudges(ctx context.Context, n int) ([]Nudge, error)
 	WriteNote(ctx context.Context, ts time.Time, text string, embedding []float32, source string) (int64, error)
 	QueryNotes(ctx context.Context, embedding []float32, k int) ([]Note, error)