feat(backend): initial setup for cms backend service

backend/src/config/env.ts

@@ -0,0 +1,51 @@
+// Environment configuration with validation
+export const env = {
+  // Database
+  DATABASE_PATH: process.env.DATABASE_PATH || './data/gallus_cms.db',
+
+  // Gitea OAuth
+  GITEA_URL: process.env.GITEA_URL || 'https://git.bookageek.ch',
+  GITEA_CLIENT_ID: process.env.GITEA_CLIENT_ID || '',
+  GITEA_CLIENT_SECRET: process.env.GITEA_CLIENT_SECRET || '',
+  GITEA_REDIRECT_URI: process.env.GITEA_REDIRECT_URI || 'http://localhost:3000/api/auth/callback',
+  GITEA_ALLOWED_USERS: process.env.GITEA_ALLOWED_USERS || '',
+
+  // Git Configuration
+  GIT_REPO_URL: process.env.GIT_REPO_URL || '',
+  GIT_TOKEN: process.env.GIT_TOKEN || '',
+  GIT_USER_NAME: process.env.GIT_USER_NAME || 'Gallus CMS',
+  GIT_USER_EMAIL: process.env.GIT_USER_EMAIL || 'cms@galluspub.ch',
+  GIT_WORKSPACE_DIR: process.env.GIT_WORKSPACE_DIR || '/tmp/gallus-repo',
+
+  // JWT & Session
+  JWT_SECRET: process.env.JWT_SECRET || '',
+  SESSION_SECRET: process.env.SESSION_SECRET || '',
+
+  // Server
+  PORT: parseInt(process.env.PORT || '3000', 10),
+  NODE_ENV: process.env.NODE_ENV || 'development',
+  CORS_ORIGIN: process.env.CORS_ORIGIN || 'http://localhost:5173',
+  FRONTEND_URL: process.env.FRONTEND_URL || 'http://localhost:5173',
+
+  // Upload
+  MAX_FILE_SIZE: parseInt(process.env.MAX_FILE_SIZE || '5242880', 10),
+};
+
+// Validate required environment variables
+export function validateEnv() {
+  const required = [
+    'DATABASE_PATH',
+    'GITEA_CLIENT_ID',
+    'GITEA_CLIENT_SECRET',
+    'GIT_REPO_URL',
+    'GIT_TOKEN',
+    'JWT_SECRET',
+    'SESSION_SECRET',
+  ];
+
+  const missing = required.filter(key => !env[key as keyof typeof env]);
+
+  if (missing.length > 0) {
+    throw new Error(`Missing required environment variables: ${missing.join(', ')}`);
+  }
+}