Add DATABASE_URL parsing for Dokku compatibility

- Parse DATABASE_URL environment variable (postgres://...)
- Dokku sets this via postgres:link command
- Falls back to individual env vars if DATABASE_URL not set

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/config/config.go

@@ -2,7 +2,9 @@ package config
 
 import (
 	"fmt"
+	"net/url"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 
@@ -96,6 +98,34 @@ func Load() (*Config, error) {
 	// Set defaults
 	setDefaults()
 
+	// Parse DATABASE_URL if set (Dokku-style)
+	dbConfig := DatabaseConfig{
+		Host:         viper.GetString("DB_HOST"),
+		Port:         viper.GetInt("DB_PORT"),
+		User:         viper.GetString("POSTGRES_USER"),
+		Password:     viper.GetString("POSTGRES_PASSWORD"),
+		Database:     viper.GetString("POSTGRES_DB"),
+		SSLMode:      viper.GetString("DB_SSLMODE"),
+		MaxOpenConns: viper.GetInt("DB_MAX_OPEN_CONNS"),
+		MaxIdleConns: viper.GetInt("DB_MAX_IDLE_CONNS"),
+		MaxLifetime:  viper.GetDuration("DB_MAX_LIFETIME"),
+	}
+
+	// Override with DATABASE_URL if present
+	if databaseURL := viper.GetString("DATABASE_URL"); databaseURL != "" {
+		parsed, err := parseDatabaseURL(databaseURL)
+		if err == nil {
+			dbConfig.Host = parsed.Host
+			dbConfig.Port = parsed.Port
+			dbConfig.User = parsed.User
+			dbConfig.Password = parsed.Password
+			dbConfig.Database = parsed.Database
+			if parsed.SSLMode != "" {
+				dbConfig.SSLMode = parsed.SSLMode
+			}
+		}
+	}
+
 	cfg = &Config{
 		Server: ServerConfig{
 			Port:         viper.GetInt("PORT"),
@@ -103,17 +133,7 @@ func Load() (*Config, error) {
 			AllowedHosts: strings.Split(viper.GetString("ALLOWED_HOSTS"), ","),
 			Timezone:     viper.GetString("TIMEZONE"),
 		},
-		Database: DatabaseConfig{
-			Host:         viper.GetString("DB_HOST"),
-			Port:         viper.GetInt("DB_PORT"),
-			User:         viper.GetString("POSTGRES_USER"),
-			Password:     viper.GetString("POSTGRES_PASSWORD"),
-			Database:     viper.GetString("POSTGRES_DB"),
-			SSLMode:      viper.GetString("DB_SSLMODE"),
-			MaxOpenConns: viper.GetInt("DB_MAX_OPEN_CONNS"),
-			MaxIdleConns: viper.GetInt("DB_MAX_IDLE_CONNS"),
-			MaxLifetime:  viper.GetDuration("DB_MAX_LIFETIME"),
-		},
+		Database: dbConfig,
 		Redis: RedisConfig{
 			URL:      viper.GetString("REDIS_URL"),
 			Password: viper.GetString("REDIS_PASSWORD"),
@@ -239,3 +259,39 @@ func (p *PushConfig) ReadAPNSKey() (string, error) {
 
 	return string(content), nil
 }
+
+// parseDatabaseURL parses a PostgreSQL URL into DatabaseConfig
+// Format: postgres://user:password@host:port/database?sslmode=disable
+func parseDatabaseURL(databaseURL string) (*DatabaseConfig, error) {
+	u, err := url.Parse(databaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse DATABASE_URL: %w", err)
+	}
+
+	// Default port
+	port := 5432
+	if u.Port() != "" {
+		port, err = strconv.Atoi(u.Port())
+		if err != nil {
+			return nil, fmt.Errorf("invalid port in DATABASE_URL: %w", err)
+		}
+	}
+
+	// Get password
+	password, _ := u.User.Password()
+
+	// Get database name (remove leading slash)
+	database := strings.TrimPrefix(u.Path, "/")
+
+	// Get sslmode from query params
+	sslMode := u.Query().Get("sslmode")
+
+	return &DatabaseConfig{
+		Host:     u.Hostname(),
+		Port:     port,
+		User:     u.User.Username(),
+		Password: password,
+		Database: database,
+		SSLMode:  sslMode,
+	}, nil
+}