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/models/leave_wish.py

@@ -18,6 +18,11 @@ class LeaveWishCreate(BaseModel):
     workspace_id: UUID
     child_id: UUID | None = None
     name: str = Field(min_length=1, max_length=255)
+    # i18n message key when `name` came from a preset (e.g.
+    # "wishEditor.presetSommar") — see app/entities/leave_wish.py. Stored
+    # alongside the translated `name` so the frontend can re-translate it;
+    # not validated against a key catalogue here (that's a frontend concern).
+    name_message_key: str | None = Field(default=None, max_length=255)
 
     window_start_month: int = Field(ge=1, le=12)
     window_start_day: int = Field(ge=1, le=31)
@@ -46,6 +51,11 @@ class LeaveWishUpdate(BaseModel):
 
     child_id: UUID | None = None
     name: str | None = Field(None, min_length=1, max_length=255)
+    # Present + null in the payload means "clear it"; absent means "leave
+    # unchanged" (see `model_fields_set` handling in the router). The service
+    # also clears this automatically whenever `name` actually changes, so a
+    # caller can never forget to and leave a stale key pointing at old text.
+    name_message_key: str | None = Field(default=None, max_length=255)
 
     window_start_month: int | None = Field(None, ge=1, le=12)
     window_start_day: int | None = Field(None, ge=1, le=31)
@@ -71,6 +81,7 @@ class LeaveWishResponse(BaseModel):
     workspace_id: UUID
     child_id: UUID | None
     name: str
+    name_message_key: str | None
 
     window_start_month: int
     window_start_day: int
@@ -100,6 +111,7 @@ class LeaveWishResponse(BaseModel):
             workspace_id=entity.workspace_id,
             child_id=entity.child_id,
             name=entity.name,
+            name_message_key=entity.name_message_key,
             window_start_month=entity.window_start_month,
             window_start_day=entity.window_start_day,
             window_end_month=entity.window_end_month,