Show only the day's docket on the Today board and add ad hoc Now workouts

- Due-filter schedules: daily always, fixed days by weekday, one-offs on
  their date; rest days get an empty state
- Workouts with no due schedule row (ad hoc or off-day starts) now render
  as their own board rows
- The + sheet is now "New Workout" with a "When" picker; "Now" (offered
  when adding on today) skips the schedule and starts the workout directly
- Remove the times-per-week scheduling mode everywhere (enum, document,
  entity, mappers, planner, seeds, tests)

Shared/Screenshots/ScreenshotSeed.swift

@@ -66,10 +66,10 @@ enum ScreenshotSeed {
 
         // ---- Schedules (the Today board's rows, spanning two goal groups) -------
         let schedulePlans: [(routine: Routine, goal: GoalKind, recurrence: ScheduleRecurrence,
-                             weekdays: [Int]?, timesPerWeek: Int?)] = [
-            (created[0], .strength, .fixedDays, [2, 5], nil),   // Upper Body · Mon & Thu
-            (created[1], .strength, .frequency, nil, 2),        // Lower Body · 2× per week
-            (created[2], .mobility, .daily, nil, nil),          // Core · daily
+                             weekdays: [Int]?)] = [
+            (created[0], .strength, .fixedDays, [2, 5]),   // Upper Body · Mon & Thu
+            (created[1], .strength, .fixedDays, [3, 7]),   // Lower Body · Tue & Sat
+            (created[2], .mobility, .daily, nil),          // Core · daily
         ]
         // Schedules predate the history below, so the Progress tab's adherence
         // tracks cover the seeded weeks instead of starting "today".
@@ -78,7 +78,7 @@ enum ScreenshotSeed {
             context.insert(Schedule(
                 id: ULID.make(), routineID: plan.routine.id, routineName: plan.routine.name,
                 goalRaw: plan.goal.rawValue, recurrenceRaw: plan.recurrence.rawValue,
-                weekdays: plan.weekdays, timesPerWeek: plan.timesPerWeek, order: i,
+                weekdays: plan.weekdays, order: i,
                 createdAt: scheduledSince, updatedAt: scheduledSince, jsonRelativePath: ""))
         }