refactor: comprehensive code quality improvements and dev environment fixes

- Convert ProcessingStatusManager from static class to individual functions
- Refactor processSingleImport function to reduce cognitive complexity
- Fix unused parameters in database-pool.ts event handlers
- Add missing DATABASE_URL configuration to env.ts
- Add pg package and @types/pg dependencies for PostgreSQL support
- Fix tsx command execution by updating package.json scripts to use pnpm exec
- Apply biome formatting fixes for import organization

lib/env.ts

@@ -103,6 +103,10 @@ export const env = {
     5
   ),
 
+  // Database Configuration
+  DATABASE_URL: parseEnvValue(process.env.DATABASE_URL) || "",
+  DATABASE_URL_DIRECT: parseEnvValue(process.env.DATABASE_URL_DIRECT) || "",
+  
   // Database Connection Pooling
   DATABASE_CONNECTION_LIMIT: parseIntWithDefault(
     process.env.DATABASE_CONNECTION_LIMIT,
@@ -123,6 +127,10 @@ export const env = {
 export function validateEnv(): { valid: boolean; errors: string[] } {
   const errors: string[] = [];
 
+  if (!env.DATABASE_URL) {
+    errors.push("DATABASE_URL is required");
+  }
+
   if (!env.NEXTAUTH_SECRET) {
     errors.push("NEXTAUTH_SECRET is required");
   }