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/route.ts

@@ -0,0 +1,30 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getTeamMembers, createTeamMember } from "@/lib/db";
+import { revalidatePath } from "next/cache";
+
+export async function GET() {
+  const members = getTeamMembers();
+  return NextResponse.json(members);
+}
+
+export async function POST(request: NextRequest) {
+  const data = await request.json() as {
+    name: string;
+    role: string;
+    image: string;
+    instagram?: string;
+    description?: string;
+  };
+
+  if (!data.name || !data.role || !data.image) {
+    return NextResponse.json(
+      { error: "name, role, and image are required" },
+      { status: 400 }
+    );
+  }
+
+  const id = createTeamMember(data);
+  revalidatePath("/");
+
+  return NextResponse.json({ id }, { status: 201 });
+}