DOM.РФ API classifies euro-format flats (26-50м²) as rooms=2.
_SUPPLY_BATCH_SQL now maps:
rooms=2 + area<35 → 'euro-1'
rooms=2 + area<50 → 'euro-2'
before the generic rooms IN (1,2,3) branch.
Audit: 4 140 units rooms=2 + area<35 in domrf_kn_flats were inflating
the supply count for genuine 2-room apartments (median 57м²).
euro buckets have no velocity counterpart in objective_corpus_room_month
so they are filtered out of top_layouts by min_velocity.
Also extends RoomBucket Literal and room_bucket_from_flat() in
layout_signature.py with the new euro-1/euro-2 values.
Closes#271 item 8
