feat: centralize application configuration using environment variables and add dynamic CORS support

notes-api/.env.example

@@ -0,0 +1,14 @@
+# Server Configuration
+HOST=127.0.0.1
+PORT=3000
+
+# Database
+DATABASE_URL=sqlite:data.db?mode=rwc
+
+# Security
+# Generate a secure random string for production (min 64 chars recommended)
+SESSION_SECRET=k-notes-super-secret-key-must-be-at-least-64-bytes-long!!!!
+
+# CORS
+# Comma-separated list of allowed origins
+CORS_ALLOWED_ORIGINS=http://localhost:5173