fix: load board detail with tasks on select, fix progress % calculation

- select() now fetches /api/v1/boards/{id} to get tasks array (lazy, once)
- updateTaskStatus() merges response correctly (spread instead of replacing)
- Progress % in sidebar uses done_count/task_count from list summary,
  or computed from tasks array when board detail is loaded

app/templates/dashboard.html

@@ -97,7 +97,7 @@
                 'bg-green-900/50 text-green-400': b.status==='active',
                 'bg-gray-800 text-gray-500': b.status==='completed'||b.status==='archived'
               }"
-              x-text="Math.round(((b.tasks||[]).filter(t=>t.status==='done').length/Math.max(1,(b.tasks||[]).length))*100)+'%'"></span>
+              x-text="Math.round((b.tasks ? b.tasks.filter(t=>t.status==='done').length/Math.max(1,b.tasks.length) : (b.done_count||0)/Math.max(1,b.task_count||1))*100)+'%'"></span>
           </div>
         </button>
       </template>
@@ -471,6 +471,12 @@ document.addEventListener('alpine:init', () => {
     },
     async select(id) {
       this.activeId = id;
+      // fetch full board detail (includes tasks array) if not yet loaded
+      const idx = this.list.findIndex(b=>b.board_id===id);
+      if(idx>=0 && !this.list[idx].tasks) {
+        const r = await fetch(`/api/v1/boards/${id}`).then(r=>r.json());
+        this.list[idx] = {...this.list[idx], ...r};
+      }
     },
     openNewBoard() { /* TODO */ },
     openNewTask(status) { /* TODO */ },
@@ -484,7 +490,7 @@ document.addEventListener('alpine:init', () => {
       const idx = this.list.findIndex(b=>b.board_id===task.board_id);
       if(idx>=0){
         const r=await fetch(`/api/v1/boards/${task.board_id}`).then(r=>r.json());
-        this.list[idx]=r.board;
+        this.list[idx]={...this.list[idx], ...r};
       }
     }
   });