rust: No panic when current time < last for quant and reclamm

[johngrantuk]

6. QuantAMM: unchecked subtraction on the weight-interpolation window

// quantamm_pool.rs, calculate_normalized_weights
let time_since_last_update = multiplier_time - last_update_time;

Underflows when current_timestamp < last_update_time, i.e. quoting at a block that precedes the
pool's last weight update — reachable during backfills and reorg handling. Same class as line 223 in
the reCLAMM table above.

Suggested fix: saturate, or return PoolError.