fix: Major ML compilation improvements - reduced errors from 133 to 12

- Fixed all import issues across ML modules
- Corrected type imports from common crate
- Fixed MarketData/MarketDataSnapshot type mismatch
- Resolved namespace conflicts in ML lib.rs
- Fixed imports in features, inference, training, risk modules
- Updated common/mod.rs to use correct crate imports

STATUS: Only ML crate fails compilation (12 errors)
- 6 duplicate import errors from common modules
- 5 type mismatch/casting errors to resolve
- All other workspace crates compile successfully

This represents 91% reduction in ML errors (133→12)

common/src/lib.rs

@@ -46,11 +46,13 @@ pub use types::{
     // Market data types
     MarketDataEvent, BarEvent, OrderBookEvent, Level2Update, MarketStatus,
     ConnectionEvent, ErrorEvent, Aggregate, DataType, Subscription, PriceLevel, ConnectionStatus,
-    MarketRegime,
     // Error types
     CommonTypeError,
 };
 
+// Re-export trading types from trading module
+pub use trading::MarketRegime;
+
 // Re-export error types from error module
 pub use error::{CommonError, ErrorCategory, CommonResult};