feat: due dates, subtasks, and task detail page (HQ-{number} URLs)

- Schema: added due_date and subtasks JSONB columns to tasks
- API: CRUD endpoints for subtasks (/tasks/:id/subtasks)
- API: due date support in create/update task
- TaskDetailPanel: due date picker with overdue/soon badges
- TaskDetailPanel: subtask checklist with progress bar
- TaskPage: full-page task view at /task/HQ-{number}
- Dashboard: task cards link to detail page, show subtask progress & due date badges
- Migration: 0001_mighty_callisto.sql

backend/src/routes/tasks.ts

@@ -1,6 +1,6 @@
 import { Elysia, t } from "elysia";
 import { db } from "../db";
-import { tasks, type ProgressNote } from "../db/schema";
+import { tasks, type ProgressNote, type Subtask } from "../db/schema";
 import { eq, asc, desc, sql, inArray, or } from "drizzle-orm";
 import { auth } from "../lib/auth";
 
@@ -153,6 +153,8 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
           position: (maxPos[0]?.max ?? 0) + 1,
           taskNumber: nextNumber,
           projectId: body.projectId || null,
+          dueDate: body.dueDate ? new Date(body.dueDate) : null,
+          subtasks: [],
           progressNotes: [],
         })
         .returning();
@@ -190,6 +192,7 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
           ])
         ),
         projectId: t.Optional(t.Union([t.String(), t.Null()])),
+        dueDate: t.Optional(t.Union([t.String(), t.Null()])),
       }),
     }
   )
@@ -236,6 +239,8 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
       if (body.assigneeId !== undefined) updates.assigneeId = body.assigneeId;
       if (body.assigneeName !== undefined) updates.assigneeName = body.assigneeName;
       if (body.projectId !== undefined) updates.projectId = body.projectId;
+      if (body.dueDate !== undefined) updates.dueDate = body.dueDate ? new Date(body.dueDate) : null;
+      if (body.subtasks !== undefined) updates.subtasks = body.subtasks;
 
       const updated = await db
         .update(tasks)
@@ -263,10 +268,107 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
         assigneeId: t.Optional(t.Union([t.String(), t.Null()])),
         assigneeName: t.Optional(t.Union([t.String(), t.Null()])),
         projectId: t.Optional(t.Union([t.String(), t.Null()])),
+        dueDate: t.Optional(t.Union([t.String(), t.Null()])),
+        subtasks: t.Optional(t.Array(t.Object({
+          id: t.String(),
+          title: t.String(),
+          completed: t.Boolean(),
+          completedAt: t.Optional(t.String()),
+          createdAt: t.String(),
+        }))),
       }),
     }
   )
 
+  // POST add subtask - requires auth
+  .post(
+    "/:id/subtasks",
+    async ({ params, body, request, headers }) => {
+      await requireSessionOrBearer(request, headers);
+      const task = await resolveTask(params.id);
+      if (!task) throw new Error("Task not found");
+
+      const currentSubtasks = (task.subtasks || []) as Subtask[];
+      const newSubtask: Subtask = {
+        id: `st-${Date.now()}-${Math.random().toString(36).slice(2, 6)}`,
+        title: body.title,
+        completed: false,
+        createdAt: new Date().toISOString(),
+      };
+      currentSubtasks.push(newSubtask);
+
+      const updated = await db
+        .update(tasks)
+        .set({ subtasks: currentSubtasks, updatedAt: new Date() })
+        .where(eq(tasks.id, task.id))
+        .returning();
+      return updated[0];
+    },
+    {
+      params: t.Object({ id: t.String() }),
+      body: t.Object({ title: t.String() }),
+    }
+  )
+
+  // PATCH toggle subtask - requires auth
+  .patch(
+    "/:id/subtasks/:subtaskId",
+    async ({ params, body, request, headers }) => {
+      await requireSessionOrBearer(request, headers);
+      const task = await resolveTask(params.id);
+      if (!task) throw new Error("Task not found");
+
+      const currentSubtasks = (task.subtasks || []) as Subtask[];
+      const subtask = currentSubtasks.find((s) => s.id === params.subtaskId);
+      if (!subtask) throw new Error("Task not found");
+
+      if (body.completed !== undefined) {
+        subtask.completed = body.completed;
+        subtask.completedAt = body.completed ? new Date().toISOString() : undefined;
+      }
+      if (body.title !== undefined) {
+        subtask.title = body.title;
+      }
+
+      const updated = await db
+        .update(tasks)
+        .set({ subtasks: currentSubtasks, updatedAt: new Date() })
+        .where(eq(tasks.id, task.id))
+        .returning();
+      return updated[0];
+    },
+    {
+      params: t.Object({ id: t.String(), subtaskId: t.String() }),
+      body: t.Object({
+        completed: t.Optional(t.Boolean()),
+        title: t.Optional(t.String()),
+      }),
+    }
+  )
+
+  // DELETE subtask - requires auth
+  .delete(
+    "/:id/subtasks/:subtaskId",
+    async ({ params, request, headers }) => {
+      await requireSessionOrBearer(request, headers);
+      const task = await resolveTask(params.id);
+      if (!task) throw new Error("Task not found");
+
+      const currentSubtasks = (task.subtasks || []) as Subtask[];
+      const filtered = currentSubtasks.filter((s) => s.id !== params.subtaskId);
+
+      const updated = await db
+        .update(tasks)
+        .set({ subtasks: filtered, updatedAt: new Date() })
+        .where(eq(tasks.id, task.id))
+        .returning();
+      return updated[0];
+    },
+    {
+      params: t.Object({ id: t.String(), subtaskId: t.String() }),
+    }
+  )
+
   // POST add progress note - requires auth
   .post(
     "/:id/notes",