feat: migrate schema to DATE type, add test infrastructure

- Migrate due_date/next_occurrence columns from TIMESTAMPTZ to DATE
- Update serializeRow() to distinguish DATE vs TIMESTAMPTZ serialization
- Simplify frontend date parsing (no more timezone workarounds)
- Add Vitest + Testing Library test infrastructure
- Add initial date parsing/formatting unit tests
- Update package.json with dev dependencies (vitest, testing-library, jsdom)

src/app/api/kanban/route.ts

@@ -0,0 +1,64 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { Pool } from 'pg';
+
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL || 'postgresql://vixtix:vixtix_secret@localhost:5433/vixtix',
+});
+
+function serializeRow(row: Record<string, any>): Record<string, any> {
+  const toCamel = (str: string) => str.replace(/_([a-z])/g, (_, c) => c.toUpperCase());
+  const result: Record<string, any> = {};
+  for (const [key, value] of Object.entries(row)) {
+    const camelKey = toCamel(key);
+    if (value instanceof Date && !isNaN(value.getTime())) {
+      if (value.getUTCHours() === 0 && value.getUTCMinutes() === 0 && value.getUTCSeconds() === 0 && value.getUTCMilliseconds() === 0) {
+        const year = value.getUTCFullYear();
+        const month = String(value.getUTCMonth() + 1).padStart(2, '0');
+        const day = String(value.getUTCDate()).padStart(2, '0');
+        result[camelKey] = `${year}-${month}-${day}`;
+      } else {
+        result[camelKey] = value.toISOString();
+      }
+    } else {
+      result[camelKey] = value;
+    }
+  }
+  return result;
+}
+
+export async function GET(request: NextRequest) {
+  const { searchParams } = new URL(request.url);
+  const projectId = searchParams.get('project');
+
+  try {
+    let whereClause = 'parent_task_id IS NULL';
+    let params: any[] = [];
+    let paramIndex = 1;
+
+    if (projectId) {
+      whereClause += ` AND project_id = $${paramIndex++}`;
+      params.push(projectId);
+    }
+
+    const result = await pool.query(
+      `SELECT t.*, p.color as project_color, p.name as project_name
+       FROM tasks t
+       LEFT JOIN projects p ON t.project_id = p.id
+       WHERE ${whereClause}
+       ORDER BY t.sort_order`,
+      params
+    );
+
+    const rows = result.rows.map(serializeRow);
+    const grouped = {
+      todo: rows.filter((t: any) => t.status === 'todo'),
+      in_progress: rows.filter((t: any) => t.status === 'in_progress'),
+      done: rows.filter((t: any) => t.status === 'done'),
+    };
+
+    return NextResponse.json(grouped);
+  } catch (error) {
+    console.error('Error fetching kanban data:', error);
+    return NextResponse.json({ error: 'Failed to fetch kanban data' }, { status: 500 });
+  }
+}