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/app/entities/leave_wish.py

@@ -24,7 +24,7 @@ class LeaveWish:
     id: UUID
     workspace_id: UUID
     child_id: UUID | None  # None = family-wide; set = tied to that child's pools
-    name: str  # "Sommar", "Jullov"
+    name: str  # "Sommar", "Jullov" — persisted, possibly-translated display text
 
     # Recurring anchor stored as month/day ints (SQLite-friendly, no custom type).
     window_start_month: int  # 1-12
@@ -55,6 +55,16 @@ class LeaveWish:
     # completely unmodified.
     window_mode: str = "fixed"  # 'fixed' | 'flexible'
 
+    # Provenance of `name`: when a wish is created from a preset (Sommar,
+    # Jullov, Höstlov, ...) this holds the i18n message key that produced the
+    # translated string stored in `name` (e.g. "wishEditor.presetSommar").
+    # Nullable — free-typed names, and every row created before this field
+    # existed, have no key and just show `name` verbatim. Cleared by
+    # `LeaveWishService.update` the moment the user edits `name`, since a
+    # user-typed name is no longer a preset label and must never silently
+    # revert to one.
+    name_message_key: str | None = None
+
     created_at: datetime | None = None
     updated_at: datetime | None = None