chore: sync generated Rust with backend spec (interval enums)

[martinkersner]

Closes #122

Backend spec now types interval as enum for cex-candle/index-price. Regen from live spec emits CexCandleInterval + IndexPriceInterval, retypes CexCandleOptions::interval/IndexPriceOptions::interval from Option<String> to the typed enums. Fixed call sites in tests/live.rs + tests/wire_contract.rs (only "1h" was ever used, maps cleanly to _1h variant on both enums — no prior valid interval string dropped).

diffstat:

src/generated.rs       | 82 +++++++++++++++++++++++++++++++++++++++++++++-----
tests/live.rs          | 13 ++++----
tests/wire_contract.rs |  8 ++---
3 files changed, 86 insertions(+), 17 deletions(-)

make check-rust DATAMAXI_RUST=<path> passes (no drift) against the live spec.