Adds habit edit, archive, and undo log features

Enables users to update or archive habits and to undo the latest habit log.
Adds PATCH/DELETE API endpoints for habit edit and soft deletion.
Introduces UI dialogs and controls for editing and archiving habits,
as well as for undoing the most recent log entry directly from the dashboard.
Improves log statistics handling by ordering and simplifies last log detection.

app/api/habits/[id]/log/route.ts

@@ -1,7 +1,7 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { db, habits, users, habitLogs } from '@/lib/db';
 import { getTokenCookie } from '@/lib/auth/cookies';
-import { eq, and } from 'drizzle-orm';
+import { eq, and, desc } from 'drizzle-orm';
 
 async function getUserFromToken() {
   const token = await getTokenCookie();
@@ -58,3 +58,49 @@ export async function POST(request: NextRequest, { params }: { params: Promise<{
     return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
   }
 }
+
+export async function DELETE(request: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  try {
+    const { id } = await params;
+    const habitId = parseInt(id);
+
+    if (isNaN(habitId)) {
+      return NextResponse.json({ error: 'Invalid habit ID' }, { status: 400 });
+    }
+
+    const user = await getUserFromToken();
+    if (!user) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+    }
+
+    // Verify habit belongs to user
+    const habitRows = await db
+      .select()
+      .from(habits)
+      .where(and(eq(habits.id, habitId), eq(habits.userId, user.id)));
+
+    if (habitRows.length === 0) {
+      return NextResponse.json({ error: 'Habit not found' }, { status: 404 });
+    }
+
+    // Find latest log
+    const latestLog = await db
+      .select()
+      .from(habitLogs)
+      .where(eq(habitLogs.habitId, habitId))
+      .orderBy(desc(habitLogs.loggedAt))
+      .limit(1);
+
+    if (latestLog.length === 0) {
+      return NextResponse.json({ error: 'No logs to undo' }, { status: 404 });
+    }
+
+    // Delete latest log
+    await db.delete(habitLogs).where(eq(habitLogs.id, latestLog[0].id));
+
+    return NextResponse.json({ success: true });
+  } catch (error) {
+    console.error('Undo log error:', error);
+    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
+  }
+}