feat(settings): add home content customization and config injection

- Add home_content setting for custom homepage (HTML or iframe URL)
- Inject public settings into index.html to eliminate page flash
- Support ETag caching with automatic invalidation on settings update
- Add Vite plugin for dev mode settings injection
- Refactor HomeView to use appStore instead of local API calls

backend/internal/config/config.go

@@ -274,6 +274,13 @@ type DatabaseConfig struct {
 }
 
 func (d *DatabaseConfig) DSN() string {
+	// 当密码为空时不包含 password 参数，避免 libpq 解析错误
+	if d.Password == "" {
+		return fmt.Sprintf(
+			"host=%s port=%d user=%s dbname=%s sslmode=%s",
+			d.Host, d.Port, d.User, d.DBName, d.SSLMode,
+		)
+	}
 	return fmt.Sprintf(
 		"host=%s port=%d user=%s password=%s dbname=%s sslmode=%s",
 		d.Host, d.Port, d.User, d.Password, d.DBName, d.SSLMode,
@@ -285,6 +292,13 @@ func (d *DatabaseConfig) DSNWithTimezone(tz string) string {
 	if tz == "" {
 		tz = "Asia/Shanghai"
 	}
+	// 当密码为空时不包含 password 参数，避免 libpq 解析错误
+	if d.Password == "" {
+		return fmt.Sprintf(
+			"host=%s port=%d user=%s dbname=%s sslmode=%s TimeZone=%s",
+			d.Host, d.Port, d.User, d.DBName, d.SSLMode, tz,
+		)
+	}
 	return fmt.Sprintf(
 		"host=%s port=%d user=%s password=%s dbname=%s sslmode=%s TimeZone=%s",
 		d.Host, d.Port, d.User, d.Password, d.DBName, d.SSLMode, tz,