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/graphql/resolvers/articles.ts

@@ -0,0 +1,83 @@
+import { builder } from "../builder.js";
+import { ArticleType } from "../types/index.js";
+import { articles, users } from "../../db/schema/index.js";
+import { eq, and, lte, desc } from "drizzle-orm";
+
+builder.queryField("articles", (t) =>
+  t.field({
+    type: [ArticleType],
+    args: {
+      featured: t.arg.boolean(),
+      limit: t.arg.int(),
+    },
+    resolve: async (_root, args, ctx) => {
+      let query = ctx.db
+        .select()
+        .from(articles)
+        .where(lte(articles.publish_date, new Date()))
+        .orderBy(desc(articles.publish_date));
+
+      if (args.limit) {
+        query = (query as any).limit(args.limit);
+      }
+
+      const articleList = await query;
+
+      return Promise.all(
+        articleList.map(async (article: any) => {
+          let author = null;
+          if (article.author) {
+            const authorUser = await ctx.db
+              .select({
+                first_name: users.first_name,
+                last_name: users.last_name,
+                avatar: users.avatar,
+                description: users.description,
+              })
+              .from(users)
+              .where(eq(users.id, article.author))
+              .limit(1);
+            author = authorUser[0] || null;
+          }
+          return { ...article, author };
+        }),
+      );
+    },
+  }),
+);
+
+builder.queryField("article", (t) =>
+  t.field({
+    type: ArticleType,
+    nullable: true,
+    args: {
+      slug: t.arg.string({ required: true }),
+    },
+    resolve: async (_root, args, ctx) => {
+      const article = await ctx.db
+        .select()
+        .from(articles)
+        .where(and(eq(articles.slug, args.slug), lte(articles.publish_date, new Date())))
+        .limit(1);
+
+      if (!article[0]) return null;
+
+      let author = null;
+      if (article[0].author) {
+        const authorUser = await ctx.db
+          .select({
+            first_name: users.first_name,
+            last_name: users.last_name,
+            avatar: users.avatar,
+            description: users.description,
+          })
+          .from(users)
+          .where(eq(users.id, article[0].author))
+          .limit(1);
+        author = authorUser[0] || null;
+      }
+
+      return { ...article[0], author };
+    },
+  }),
+);