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/backend/src/db/schema/comments.ts

@@ -0,0 +1,30 @@
+import {
+  pgTable,
+  text,
+  timestamp,
+  index,
+  integer,
+} from "drizzle-orm/pg-core";
+import { users } from "./users.js";
+
+export const comments = pgTable(
+  "comments",
+  {
+    id: integer("id").primaryKey().generatedAlwaysAsIdentity(),
+    collection: text("collection").notNull(), // 'videos' | 'recordings'
+    item_id: text("item_id").notNull(),
+    comment: text("comment").notNull(),
+    user_id: text("user_id")
+      .notNull()
+      .references(() => users.id, { onDelete: "cascade" }),
+    date_created: timestamp("date_created").notNull().defaultNow(),
+    date_updated: timestamp("date_updated"),
+  },
+  (t) => [
+    index("comments_collection_item_idx").on(t.collection, t.item_id),
+    index("comments_user_idx").on(t.user_id),
+  ],
+);
+
+export type Comment = typeof comments.$inferSelect;
+export type NewComment = typeof comments.$inferInsert;