refactor(ml): rename real_data_loader to data_loader

The real_ prefix was misleading — there is no fake data loader.
Mechanical rename across 18 source files, no logic changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/ml/src/data_validation/rules.rs

@@ -4,7 +4,7 @@
 //! Each rule implements the `ValidationRule` trait and can be composed
 //! into a comprehensive validation pipeline.
 
-use crate::real_data_loader::Indicators;
+use crate::data_loader::Indicators;
 use crate::types::OHLCVBar;
 use anyhow::Result;
 

crates/ml/src/data_validation/validator.rs

@@ -5,7 +5,7 @@
 use std::fmt::Write as _;
 
 use super::rules::{Severity, ValidationError, ValidationRule};
-use crate::real_data_loader::Indicators;
+use crate::data_loader::Indicators;
 use crate::types::OHLCVBar;
 use anyhow::Result;
 use std::sync::atomic::{AtomicUsize, Ordering};