Show preset wish names in the current UI language

Preset wishes were created with `name: t(preset.labelKey)`, so the
translated string was persisted as the wish's name. A wish created while
the UI was Swedish stayed "Jul" in English forever -- the Swedish text
was the data, so no display-layer change could fix it.

Wish names are user-editable free text, so `name` cannot simply be
translated at render time. Migration 007 adds a nullable
`leave_wish.name_message_key` recording where a name came from: preset
wishes store the i18n key alongside the translated literal, and the UI
renders the key when present.

The key is cleared server-side the moment `name` actually changes,
compared against the stored value rather than trusting the caller, so no
client can forget to clear it and silently revert a user's own name to a
preset label.

An unknown key (a stale row, a renamed key) falls back to the stored
literal via an isTranslationKey guard, so a bad key can never crash the
page or leak a raw key to the user. Rows predating this column keep
displaying their stored name.

_FULL_SCHEMA in db/connection.py is updated in step with the migration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RXMhc9nT6sNz1SL4j8dznL

backend/migrations/versions/007_add_leave_wish_name_message_key.py

@@ -0,0 +1,51 @@
+"""Add leave_wish.name_message_key (nullable i18n key for preset names).
+
+Bug: `WishEditor.tsx` created preset wishes (Sommar/Jullov/Höstlov/...) with
+`name` set to the already-translated string (e.g. "Jul"), persisted as-is.
+Switching the UI language afterwards could never fix a wish's name, because
+the Swedish (or English) text was the data, not a rendering choice.
+
+Fix: `name_message_key` stores the i18n key that produced `name` at creation
+time (e.g. "wishEditor.seasonJul"), alongside the translated `name` so
+anything reading `name` directly (backend, exports, ...) still gets a sane
+value. The frontend re-translates via the key when present and falls back to
+the literal `name` otherwise. Nullable and no default: every existing row
+(and any row created by a free-typed custom name) has no key and must keep
+showing its stored `name` unchanged — see `LeaveWishService.update`, which
+also force-clears the key the moment a user edits `name`.
+
+Revision ID: 007
+Revises: 006
+Create Date: 2026-09-14
+"""
+
+from __future__ import annotations
+
+from alembic import op
+
+revision: str = "007"
+down_revision: str | None = "006"
+branch_labels: str | None = None
+depends_on: str | None = None
+
+_UPGRADE_SQL = """
+ALTER TABLE leave_wish ADD COLUMN name_message_key TEXT;
+"""
+
+_DOWNGRADE_SQL = """
+ALTER TABLE leave_wish DROP COLUMN name_message_key;
+"""
+
+
+def upgrade() -> None:
+    from sqlalchemy import text
+
+    for stmt in [s.strip() for s in _UPGRADE_SQL.split(";") if s.strip()]:
+        op.execute(text(stmt))
+
+
+def downgrade() -> None:
+    from sqlalchemy import text
+
+    for stmt in [s.strip() for s in _DOWNGRADE_SQL.split(";") if s.strip()]:
+        op.execute(text(stmt))