feat: add master classes section with registration system

- New master classes section on landing page with upcoming events grid
- Admin CRUD for master classes (image, slots, trainer, style, cost, location)
- User signup modal (name + Instagram required, Telegram optional)
- Admin registration management: view, add, edit, delete with quick-contact links
- Customizable success message for signup confirmation
- Auto-filter past events, Russian date formatting, duration auto-calculation

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

src/lib/db.ts

@@ -26,6 +26,15 @@ function initTables(db: Database.Database) {
       updated_at TEXT DEFAULT (datetime('now'))
     );
 
+    CREATE TABLE IF NOT EXISTS mc_registrations (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      master_class_title TEXT NOT NULL,
+      name TEXT NOT NULL,
+      instagram TEXT NOT NULL,
+      telegram TEXT,
+      created_at TEXT DEFAULT (datetime('now'))
+    );
+
     CREATE TABLE IF NOT EXISTS team_members (
       id INTEGER PRIMARY KEY AUTOINCREMENT,
       name TEXT NOT NULL,
@@ -228,6 +237,7 @@ const SECTION_KEYS = [
   "hero",
   "about",
   "classes",
+  "masterClasses",
   "faq",
   "pricing",
   "schedule",
@@ -257,6 +267,7 @@ export function getSiteContent(): SiteContent | null {
     hero: sections.hero,
     about: sections.about,
     classes: sections.classes,
+    masterClasses: sections.masterClasses ?? { title: "Мастер-классы", items: [] },
     faq: sections.faq,
     pricing: sections.pricing,
     schedule: sections.schedule,
@@ -276,4 +287,74 @@ export function isDatabaseSeeded(): boolean {
   return row.count > 0;
 }
 
+// --- MC Registrations ---
+
+interface McRegistrationRow {
+  id: number;
+  master_class_title: string;
+  name: string;
+  instagram: string;
+  telegram: string | null;
+  created_at: string;
+}
+
+export interface McRegistration {
+  id: number;
+  masterClassTitle: string;
+  name: string;
+  instagram: string;
+  telegram?: string;
+  createdAt: string;
+}
+
+export function addMcRegistration(
+  masterClassTitle: string,
+  name: string,
+  instagram: string,
+  telegram?: string
+): number {
+  const db = getDb();
+  const result = db
+    .prepare(
+      `INSERT INTO mc_registrations (master_class_title, name, instagram, telegram)
+       VALUES (?, ?, ?, ?)`
+    )
+    .run(masterClassTitle, name, instagram, telegram || null);
+  return result.lastInsertRowid as number;
+}
+
+export function getMcRegistrations(masterClassTitle: string): McRegistration[] {
+  const db = getDb();
+  const rows = db
+    .prepare(
+      "SELECT * FROM mc_registrations WHERE master_class_title = ? ORDER BY created_at DESC"
+    )
+    .all(masterClassTitle) as McRegistrationRow[];
+  return rows.map((r) => ({
+    id: r.id,
+    masterClassTitle: r.master_class_title,
+    name: r.name,
+    instagram: r.instagram,
+    telegram: r.telegram ?? undefined,
+    createdAt: r.created_at,
+  }));
+}
+
+export function updateMcRegistration(
+  id: number,
+  name: string,
+  instagram: string,
+  telegram?: string
+): void {
+  const db = getDb();
+  db.prepare(
+    "UPDATE mc_registrations SET name = ?, instagram = ?, telegram = ? WHERE id = ?"
+  ).run(name, instagram, telegram || null, id);
+}
+
+export function deleteMcRegistration(id: number): void {
+  const db = getDb();
+  db.prepare("DELETE FROM mc_registrations WHERE id = ?").run(id);
+}
+
 export { SECTION_KEYS };