🔧 feat: update configuration defaults and add environment variables s…

…upport

The commit message is too long to fit in a single line, so I'll split it into subject and body:

🔧 feat: update security and performance defaults in configuration

• Reduce max upload size from 50MB to 5MB for better resource management
• Lower rate limit from 60 to 10 requests per minute
• Add environment variables support with 0X prefix
• Update SMTP configuration documentation for PostPilot integration

config/config.yaml

@@ -36,13 +36,13 @@ server:
   # Public-facing URL (used for generating links)
   base_url: http://localhost:3000
 
-  # Maximum upload size in bytes (default: 50MB)
-  max_upload_size: 52428800  # 50 * 1024 * 1024
+  # Maximum upload size in bytes (default: 5MB)
+  max_upload_size: 5242880  # 5 * 1024 * 1024
 
   # Rate limiting configuration
   rate_limit:
     enabled: true
-    requests: 60    # Number of requests
+    requests: 10    # Number of requests
     duration: 60    # Time window in seconds
 
   # Security settings
@@ -68,7 +68,7 @@ server:
     interval: 3600   # Cleanup interval in seconds
     max_age: 168h    # Maximum age for temporary pastes (7 days)
 
-# SMTP configuration for sending emails
+# SMTP configuration for sending emails with PostPilot
 smtp:
   enabled: true  # Set to true to enable email features
   host: localhost

internal/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/spf13/viper"
 )
@@ -64,7 +65,7 @@ func Load() (*Config, error) {
 	viper.SetDefault("storage.type", "local")
 	viper.SetDefault("storage.path", "./uploads")
 	viper.SetDefault("server.address", ":3000")
-	viper.SetDefault("server.max_upload_size", 50*1024*1024) // 50MB default
+	viper.SetDefault("server.max_upload_size", 5*1024*1024) // 5MB default
 	viper.SetDefault("server.cleanup.enabled", true)
 	viper.SetDefault("server.cleanup.interval", 3600)
 	viper.SetDefault("server.cleanup.max_age", "168h")
@@ -76,6 +77,11 @@ func Load() (*Config, error) {
 	viper.SetDefault("smtp.tls_verify", true)
 	viper.SetDefault("smtp.from_name", "Paste69")
 
+	// Enable environment variables
+	viper.AutomaticEnv()
+	viper.SetEnvPrefix("0X")
+	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_")) // Converts nested keys to env format
+
 	if err := viper.ReadInConfig(); err != nil {
 		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
 			return nil, fmt.Errorf("error reading config file: %w", err)