Align board-specific stock order sizing

crates/fidc-core/src/instrument.rs

@@ -20,6 +20,21 @@ impl Instrument {
         self.round_lot.max(1)
     }
 
+    pub fn minimum_order_quantity(&self) -> u32 {
+        match self.board.trim().to_ascii_uppercase().as_str() {
+            "KSH" => 200,
+            "BJS" | "BJ" | "BJSE" => 100,
+            _ => self.effective_round_lot(),
+        }
+    }
+
+    pub fn order_step_size(&self) -> u32 {
+        match self.board.trim().to_ascii_uppercase().as_str() {
+            "KSH" | "BJS" | "BJ" | "BJSE" => 1,
+            _ => self.effective_round_lot(),
+        }
+    }
+
     pub fn is_delisted_before(&self, date: NaiveDate) -> bool {
         self.delisted_at
             .is_some_and(|delisted_at| delisted_at < date)