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/directus.ts

@@ -1,35 +1,3 @@
-import { authentication, createDirectus, rest } from "@directus/sdk";
-import { env } from "$env/dynamic/public";
-import type { CurrentUser } from "./types";
-
-export const directusApiUrl = env.PUBLIC_API_URL || "http://localhost:3000/api";
-
-export const getDirectusInstance = (fetch?: typeof globalThis.fetch) => {
-	const options: { globals?: { fetch: typeof globalThis.fetch } } = fetch
-		? { globals: { fetch } }
-		: {};
-	const directus = createDirectus(directusApiUrl, options)
-		.with(rest())
-		.with(authentication("session"));
-	return directus;
-};
-
-export const getAssetUrl = (
-	id: string,
-	transform?: "mini" | "thumbnail" | "preview" | "medium" | "banner",
-) => {
-	if (!id) {
-		return null;
-	}
-	return `${directusApiUrl}/assets/${id}${transform ? "?key=" + transform : ""}`;
-};
-
-export const isModel = (user: CurrentUser) => {
-	if (user.role.name === "Model") {
-		return true;
-	}
-	if (user.policies.find((p) => p.policy.name === "Model")) {
-		return true;
-	}
-	return false;
-};
+// Re-export from api.ts for backwards compatibility
+// All components that import from $lib/directus continue to work
+export { apiUrl as directusApiUrl, getAssetUrl, isModel, getGraphQLClient as getDirectusInstance } from "./api.js";