If #4866 is successful, migrate all GTFS dimensional models (mart_gtfs.dim_*) to use microbatch incremental strategy instead of merge.

Acceptance criteria:

• Check costs to turn off incremental on everything besides stops, shapes, trips. Either migrate all models or just the big ones and turn off incremental on the rest.
• Document the DBT_ALL_MICROBATCH_LOOKBACK_DAYS dbt variable.
• Update the microbatch partitions notebook to use uv instead of poetry