Retrait des compétences ; disponibilités en fenêtres horaires libres

Compétences supprimées de bout en bout :
- tables `skill`, `volunteer_skill`, `shift_required_skill` ;
- `Volunteer.skill_codes`, `Shift.required_skill_codes`, colonne `skills`
  de l'import, règle de validation `MISSING_REQUIRED_SKILL`, jeu de démo.

Disponibilités repensées : `Availability` passe de (`day_part_id`,
`status` tri-état) à une **fenêtre horaire libre** (`date`, `start_time`,
`end_time` ; `end <= start` ⇒ passe minuit), plusieurs par jour.
- Nouveaux endpoints `GET`/`PUT /editions/{id}/volunteers/{vid}/availability`
  (PUT = remplacement complet, COORDINATION) et
  `GET /editions/{id}/availability` (toute l'édition, pour la grille).
- `OUTSIDE_AVAILABILITY` (toujours WARNING) : compare le créneau à l'union
  des fenêtres du bénévole ce jour-là ; renvoie `date` + `uncovered_minutes`.
  `DayPart` ne sert plus qu'à la borne de « journée » du cumul 8 h.
- L'import ne gère plus les disponibilités (fenêtres saisies dans l'app) :
  `values.py` supprimé, mapping réduit à nom/email/téléphone/commentaire.

Migration 0007 (recrée `availability`). `AvailabilityStatus` supprimé.
158 tests, `alembic check` et `ruff` au vert. Front à suivre.

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

backend/app/migrations/versions/0007_drop_skills_avail_windows.py

@@ -0,0 +1,155 @@
+"""Retrait des compétences ; disponibilités en fenêtres horaires libres
+
+Revision ID: 0007_drop_skills_avail_windows
+Revises: 0006_artist_and_volunteer_wishes
+Create Date: 2026-09-10
+
+- Suppression des tables `skill`, `volunteer_skill`, `shift_required_skill`.
+- `availability` : on abandonne (`day_part_id`, `status`) au profit de
+  (`start_time`, `end_time`) — fenêtre horaire libre, plusieurs par jour.
+  La table est recréée (les anciennes lignes ne sont pas convertibles).
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0007_drop_skills_avail_windows"
+down_revision: str | None = "0006_artist_and_volunteer_wishes"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+_STATUS = sa.Enum(
+    "AVAILABLE", "IF_NEEDED", "UNAVAILABLE",
+    name="availabilitystatus", native_enum=False,
+)
+
+
+def upgrade() -> None:
+    op.drop_table("shift_required_skill")
+    op.drop_table("volunteer_skill")
+    op.drop_index("ix_skill_edition_id", table_name="skill")
+    op.drop_table("skill")
+
+    op.drop_table("availability")
+    op.create_table(
+        "availability",
+        sa.Column("created_at", sa.DateTime(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(), nullable=False),
+        sa.Column("id", sa.Uuid(), nullable=False),
+        sa.Column("edition_id", sa.Uuid(), nullable=False),
+        sa.Column("volunteer_id", sa.Uuid(), nullable=False),
+        sa.Column("date", sa.Date(), nullable=False),
+        sa.Column("start_time", sa.Time(), nullable=False),
+        sa.Column("end_time", sa.Time(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["edition_id"], ["edition.id"], ondelete="CASCADE"
+        ),
+        sa.ForeignKeyConstraint(
+            ["volunteer_id"], ["volunteer.id"], ondelete="CASCADE"
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "volunteer_id", "date", "start_time", "end_time",
+            name="uq_availability_window",
+        ),
+    )
+    op.create_index(
+        op.f("ix_availability_edition_id"),
+        "availability",
+        ["edition_id"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_availability_volunteer_id"),
+        "availability",
+        ["volunteer_id"],
+        unique=False,
+    )
+
+
+def downgrade() -> None:
+    op.drop_index(op.f("ix_availability_volunteer_id"), table_name="availability")
+    op.drop_index(op.f("ix_availability_edition_id"), table_name="availability")
+    op.drop_table("availability")
+    op.create_table(
+        "availability",
+        sa.Column("created_at", sa.DateTime(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(), nullable=False),
+        sa.Column("id", sa.Uuid(), nullable=False),
+        sa.Column("edition_id", sa.Uuid(), nullable=False),
+        sa.Column("volunteer_id", sa.Uuid(), nullable=False),
+        sa.Column("date", sa.Date(), nullable=False),
+        sa.Column("day_part_id", sa.Uuid(), nullable=False),
+        sa.Column("status", _STATUS, nullable=False),
+        sa.ForeignKeyConstraint(
+            ["edition_id"], ["edition.id"], ondelete="CASCADE"
+        ),
+        sa.ForeignKeyConstraint(
+            ["volunteer_id"], ["volunteer.id"], ondelete="CASCADE"
+        ),
+        sa.ForeignKeyConstraint(
+            ["day_part_id"], ["day_part.id"], ondelete="CASCADE"
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "volunteer_id", "date", "day_part_id", name="uq_availability_slot"
+        ),
+    )
+    op.create_index(
+        op.f("ix_availability_edition_id"),
+        "availability", ["edition_id"], unique=False,
+    )
+    op.create_index(
+        op.f("ix_availability_volunteer_id"),
+        "availability", ["volunteer_id"], unique=False,
+    )
+    op.create_index(
+        op.f("ix_availability_day_part_id"),
+        "availability", ["day_part_id"], unique=False,
+    )
+
+    op.create_table(
+        "skill",
+        sa.Column("created_at", sa.DateTime(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(), nullable=False),
+        sa.Column("id", sa.Uuid(), nullable=False),
+        sa.Column("edition_id", sa.Uuid(), nullable=False),
+        sa.Column("code", sa.String(), nullable=False),
+        sa.Column("label", sa.String(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["edition_id"], ["edition.id"], ondelete="CASCADE"
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "edition_id", "code", name="uq_skill_edition_code"
+        ),
+    )
+    op.create_index(
+        op.f("ix_skill_edition_id"), "skill", ["edition_id"], unique=False
+    )
+    op.create_table(
+        "volunteer_skill",
+        sa.Column("volunteer_id", sa.Uuid(), nullable=False),
+        sa.Column("skill_id", sa.Uuid(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["skill_id"], ["skill.id"], ondelete="CASCADE"
+        ),
+        sa.ForeignKeyConstraint(
+            ["volunteer_id"], ["volunteer.id"], ondelete="CASCADE"
+        ),
+        sa.PrimaryKeyConstraint("volunteer_id", "skill_id"),
+    )
+    op.create_table(
+        "shift_required_skill",
+        sa.Column("shift_id", sa.Uuid(), nullable=False),
+        sa.Column("skill_id", sa.Uuid(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["shift_id"], ["shift.id"], ondelete="CASCADE"
+        ),
+        sa.ForeignKeyConstraint(
+            ["skill_id"], ["skill.id"], ondelete="CASCADE"
+        ),
+        sa.PrimaryKeyConstraint("shift_id", "skill_id"),
+    )