feat: admin panel with SQLite, auth, and calendar-style schedule editor

Complete admin panel for content management:
- SQLite database with better-sqlite3, seed script from content.ts
- Simple password auth with HMAC-signed cookies (Edge + Node compatible)
- 9 section editors: meta, hero, about, team, classes, schedule, pricing, FAQ, contact
- Team CRUD with image upload and drag reorder
- Schedule editor with Google Calendar-style visual timeline (colored blocks, overlap detection, click-to-add)
- All public components refactored to accept data props from DB (with fallback to static content)
- Middleware protecting /admin/* and /api/admin/* routes

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

src/app/api/admin/team/[id]/route.ts

@@ -0,0 +1,29 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getTeamMember, updateTeamMember, deleteTeamMember } from "@/lib/db";
+import { revalidatePath } from "next/cache";
+
+type Params = { params: Promise<{ id: string }> };
+
+export async function GET(_request: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const member = getTeamMember(Number(id));
+  if (!member) {
+    return NextResponse.json({ error: "Not found" }, { status: 404 });
+  }
+  return NextResponse.json(member);
+}
+
+export async function PUT(request: NextRequest, { params }: Params) {
+  const { id } = await params;
+  const data = await request.json();
+  updateTeamMember(Number(id), data);
+  revalidatePath("/");
+  return NextResponse.json({ ok: true });
+}
+
+export async function DELETE(_request: NextRequest, { params }: Params) {
+  const { id } = await params;
+  deleteTeamMember(Number(id));
+  revalidatePath("/");
+  return NextResponse.json({ ok: true });
+}