revert(lookup): restore PARTITION BY group; tests now track data fix

Reverts the PARTITION BY name change — group is the correct dedup key.
Partitioning by name broke country deduplication (two US records both
survived, causing Svelte each_key_duplicate on alpha_2_code='US').

Root cause is bad seed data in lu_v3_time_zone: group='United States'
for 13 US/* zones and group='Europe' for 63 Europe/* zones instead of
group=name. A separate DB UPDATE is required to fix those rows.

Tests updated to assert:
- No duplicate alpha_2_code in country list (PARTITION BY group regression)
- All 13 US/* and Europe/* spot-check zones present (pending DB data fix)
- priority-only timezone count == 72 (pending DB data fix)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/methods/lookup_methods.py

@@ -28,7 +28,7 @@ def get_lookup_list_v3(
         SELECT * FROM (
             SELECT *, 
                    ROW_NUMBER() OVER (
-                       PARTITION BY `name`
+                       PARTITION BY `group`
                        ORDER BY
                           (for_type = :for_type AND for_id = :for_id) DESC,
                           (account_id = :account_id) DESC,