fix: ensure manually tagged faces have proper source type (#16364)

immich-app/immich#16062 added manual face tagging and deletion, but did
not add a new 'SourceType'. The create faces would default to
'machine-learning' which is incorrect, and has the annoying downside
that they will be wiped when the 'Refresh Faces' job is run.

Handling of non-machine-learning faces was previously added in
immich-app/immich#6455. This PR simply extends it to the new manually
tagged faces.

server/src/enum.ts

@@ -228,6 +228,7 @@ export enum AssetStatus {
 export enum SourceType {
   MACHINE_LEARNING = 'machine-learning',
   EXIF = 'exif',
+  MANUAL = 'manual',
 }
 
 export enum ManualJobName {