Function normalize_ts_to_ms 

pub fn normalize_ts_to_ms(ts: i64) -> i64

Normalize a raw exchange timestamp to UTC milliseconds.

Heuristic based on digit count of the absolute value:

• ≤ 10 digits (≤ 9_999_999_999) → seconds → × 1_000
• 13 digits (10_000_000_000 to 9_999_999_999_999) → milliseconds → identity
• 16 digits → microseconds → ÷ 1_000
• ≥ 19 digits → nanoseconds → ÷ 1_000_000
• Zero or negative below seconds range → 0