Remove school day hours from schedule templates

The day progress bar no longer uses day start/end times (it uses block
durations instead), so the field is no longer needed.

Removed from: Admin UI, schedule store, schedule model/schemas/router,
session broadcast payload, dashboard snapshot, and startup migrations.
DB columns are left in place (harmless, no migration required).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/stores/schedule.js

@@ -11,8 +11,6 @@ export const useScheduleStore = defineStore('schedule', () => {
   const blockStartedAt = ref(null)    // Date.now() ms when current counting period started
   const blockElapsedOffset = ref(0)   // seconds already elapsed before blockStartedAt
   const blockElapsedCache = ref({})   // blockId → total elapsed seconds (survives block switches)
-  const dayStartTime = ref(null)      // "HH:MM:SS" string or null
-  const dayEndTime = ref(null)        // "HH:MM:SS" string or null
   const morningRoutine = ref([])      // list of text strings shown during greeting state
   const breakActivities = ref([])     // list of text strings shown during break time
   // Break timer state (per-block break time at end of block)
@@ -45,8 +43,6 @@ export const useScheduleStore = defineStore('schedule', () => {
     completedBlockIds.value = snapshot.completed_block_ids || []
     isPaused.value = snapshot.is_paused || false
     if (snapshot.child) child.value = snapshot.child
-    dayStartTime.value = snapshot.day_start_time || null
-    dayEndTime.value = snapshot.day_end_time || null
     morningRoutine.value = snapshot.morning_routine || []
     breakActivities.value = snapshot.break_activities || []
     // Restore elapsed time from server-computed value and seed the per-block cache
@@ -86,8 +82,6 @@ export const useScheduleStore = defineStore('schedule', () => {
       blockStartedAt.value = null
       blockElapsedOffset.value = 0
       blockElapsedCache.value = {}
-      dayStartTime.value = null
-      dayEndTime.value = null
       isBreakMode.value = false
       breakStartedAt.value = null
       breakElapsedOffset.value = 0
@@ -322,8 +316,6 @@ export const useScheduleStore = defineStore('schedule', () => {
     blockStartedAt,
     blockElapsedOffset,
     blockElapsedCache,
-    dayStartTime,
-    dayEndTime,
     morningRoutine,
     breakActivities,
     isBreakMode,