Bénévole : retrait de la taille de t-shirt et du régime alimentaire

Champs `tshirt_size` et `diet` supprimés du modèle `Volunteer`, des schémas
d'API, de l'import CSV/Excel (mapping, suggestions, exécution) et du jeu de
démonstration. Énum `TshirtSize` et helper `parse_tshirt_size` supprimés.
Migration 0005. Clé i18n `import.row.invalid_tshirt_size` retirée.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017uUsRg7XzopkCPWimwg9ZM

backend/tests/test_import_values.py

@@ -1,8 +1,8 @@
 import pytest
 
 from app.importing.text import slug_code, split_skills
-from app.importing.values import parse_availability_cell, parse_tshirt_size
-from app.models import AvailabilityStatus, TshirtSize
+from app.importing.values import parse_availability_cell
+from app.models import AvailabilityStatus
 
 
 @pytest.mark.parametrize(
@@ -32,24 +32,6 @@ def test_unknown_cell_is_flagged():
     assert parse_availability_cell("bof") == (None, False)
 
 
-@pytest.mark.parametrize(
-    ("raw", "expected"),
-    [
-        ("M", TshirtSize.M),
-        (" m ", TshirtSize.M),
-        ("xl", TshirtSize.XL),
-        ("2XL", TshirtSize.XXL),
-        ("3 XL", TshirtSize.XXXL),
-    ],
-)
-def test_tshirt_sizes(raw, expected):
-    assert parse_tshirt_size(raw) is expected
-
-
-def test_unknown_tshirt_size_is_none():
-    assert parse_tshirt_size("large") is None
-
-
 def test_slug_code_is_stable_across_accents_and_case():
     assert slug_code("Régie son") == "REGIE_SON"
     assert slug_code(" permis B ") == "PERMIS_B"