Move 3 Strikes from Admin to Dashboard, add strikes feature

- Adds strikes (0-3) to Child model with migration
- New PATCH /api/children/{id}/strikes endpoint with WebSocket broadcast
- TV dashboard shows red ✕ marks next to child name when strikes > 0
- 3 Strikes card on Dashboard page (removed from Admin)

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

frontend/src/views/TVView.vue

@@ -2,7 +2,16 @@
   <div class="tv-root">
     <!-- Header bar -->
     <header class="tv-header">
-      <div class="tv-child-name">{{ scheduleStore.child?.name || 'Loading...' }}</div>
+      <div class="tv-child-name-wrap">
+        <div class="tv-child-name">{{ scheduleStore.child?.name || 'Loading...' }}</div>
+        <div class="tv-strikes" v-if="scheduleStore.child?.strikes > 0">
+          <span
+            v-for="i in scheduleStore.child.strikes"
+            :key="i"
+            class="tv-strike-x"
+          >✕</span>
+        </div>
+      </div>
       <div class="tv-clock">{{ clockDisplay }}</div>
       <div class="tv-date">{{ dateDisplay }}</div>
     </header>
@@ -197,12 +206,30 @@ onMounted(async () => {
   padding-bottom: 1rem;
 }
 
+.tv-child-name-wrap {
+  display: flex;
+  align-items: center;
+  gap: 1rem;
+}
+
 .tv-child-name {
   font-size: 2.5rem;
   font-weight: 700;
   color: #818cf8;
 }
 
+.tv-strikes {
+  display: flex;
+  gap: 0.4rem;
+}
+
+.tv-strike-x {
+  font-size: 2rem;
+  font-weight: 700;
+  color: #ef4444;
+  line-height: 1;
+}
+
 .tv-clock {
   font-size: 3rem;
   font-weight: 300;