[router] add centralized configuration module for sgl-router (#7588)

sgl-router/src/config/mod.rs

@@ -0,0 +1,28 @@
+pub mod types;
+pub mod validation;
+
+pub use types::*;
+pub use validation::*;
+
+/// Configuration errors
+#[derive(Debug, thiserror::Error)]
+pub enum ConfigError {
+    #[error("Validation failed: {reason}")]
+    ValidationFailed { reason: String },
+
+    #[error("Invalid value for field '{field}': {value} - {reason}")]
+    InvalidValue {
+        field: String,
+        value: String,
+        reason: String,
+    },
+
+    #[error("Incompatible configuration: {reason}")]
+    IncompatibleConfig { reason: String },
+
+    #[error("Missing required field: {field}")]
+    MissingRequired { field: String },
+}
+
+/// Result type for configuration operations
+pub type ConfigResult<T> = Result<T, ConfigError>;