feat: migrate from Next.js Pages Router to App Router with Payload CMS

Complete architectural overhaul migrating from Directus+tRPC to Payload CMS with Next.js App Router. This represents a fundamental shift in how the application is structured and how data is managed.

Major changes:
- Migrated from Pages Router (src/pages/) to App Router (src/app/)
- Replaced Directus CMS with Payload CMS as the content management system
- Removed tRPC in favor of Payload's built-in API routes
- Added PostgreSQL database via Docker Compose for local development
- Implemented separate route groups for frontend and Payload admin
- Updated all API routes to App Router conventions
- Added Payload collections for Projects, Technologies, Links, Media, and Users
- Configured ESLint for new project structure

Infrastructure:
- Added docker-compose.yml for PostgreSQL database
- Updated environment variables for Payload CMS configuration
- Integrated @payloadcms/next for seamless Next.js integration
- Added GraphQL API and playground routes

Dependencies:
- Upgraded React from 18.2.0 to 19.2.0
- Upgraded Next.js to 15.5.6
- Added Payload CMS 3.x packages (@payloadcms/db-postgres, @payloadcms/next, etc.)
- Removed Directus SDK and tRPC packages
- Updated Sharp to 0.34.x
- Migrated to @tanstack/react-query v5

eslint.config.js

@@ -0,0 +1,24 @@
+import { dirname } from "path";
+import { fileURLToPath } from "url";
+import { FlatCompat } from "@eslint/eslintrc";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+});
+
+const eslintConfig = [
+  ...compat.extends("next/core-web-vitals"),
+  {
+    ignores: [
+      ".next/**",
+      "out/**",
+      "build/**",
+      "next-env.d.ts",
+    ],
+  },
+];
+
+export default eslintConfig;