feat: replace Directus with custom Node.js GraphQL backend

Removes Directus 11 and replaces it with a lean, purpose-built backend:
- packages/backend/: Fastify v5 + GraphQL Yoga v5 + Pothos (code-first)
  with Drizzle ORM, Redis sessions (session_token cookie), argon2 auth,
  Nodemailer, fluent-ffmpeg, and full gamification system ported from bundle
- Frontend: @directus/sdk replaced by graphql-request v7; services.ts fully
  rewritten with identical signatures; directus.ts now re-exports from api.ts
- Cookie renamed directus_session_token → session_token
- Dev proxy target updated 8055 → 4000
- compose.yml: Directus service removed, backend service added (port 4000)
- Dockerfile.backend: new multi-stage image with ffmpeg
- Dockerfile: bundle build step and ffmpeg removed from frontend image
- data-migration.ts: one-time script to migrate all Directus/sexy_ tables

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

packages/frontend/src/lib/api.ts

@@ -0,0 +1,25 @@
+import { GraphQLClient } from "graphql-request";
+import { env } from "$env/dynamic/public";
+import type { CurrentUser } from "./types";
+
+export const apiUrl = env.PUBLIC_API_URL || "http://localhost:3000/api";
+
+export const getGraphQLClient = (fetchFn?: typeof globalThis.fetch) =>
+  new GraphQLClient(`${apiUrl}/graphql`, {
+    credentials: "include",
+    fetch: fetchFn || globalThis.fetch,
+  });
+
+export const getAssetUrl = (
+  id: string,
+  transform?: "mini" | "thumbnail" | "preview" | "medium" | "banner",
+) => {
+  if (!id) {
+    return null;
+  }
+  return `${apiUrl}/assets/${id}${transform ? "?transform=" + transform : ""}`;
+};
+
+export const isModel = (user: CurrentUser) => {
+  return user.role === "model";
+};