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/app/api/schemas.py

@@ -9,7 +9,6 @@ from app.models import (
     AssignmentSource,
     PositionCategory,
     Role,
-    TshirtSize,
 )
 from app.validation import Violation
 
@@ -49,8 +48,6 @@ class VolunteerCreate(ApiModel):
     last_name: str
     email: str | None = None
     phone: str | None = None
-    tshirt_size: TshirtSize | None = None
-    diet: str | None = None
     comment: str | None = None
     skill_codes: list[str] = Field(default_factory=list)
 
@@ -60,8 +57,6 @@ class VolunteerUpdate(ApiModel):
     last_name: str | None = None
     email: str | None = None
     phone: str | None = None
-    tshirt_size: TshirtSize | None = None
-    diet: str | None = None
     comment: str | None = None
     # None = inchangé ; [] = vider les compétences.
     skill_codes: list[str] | None = None
@@ -74,8 +69,6 @@ class VolunteerRead(ApiModel):
     last_name: str
     email: str | None
     phone: str | None
-    tshirt_size: TshirtSize | None
-    diet: str | None
     comment: str | None
     skill_codes: list[str]
     created_at: dt.datetime