feat: external lunch attendees card + dialog

Adds program.listFinalistProjects helper. Externals dialog supports
both standalone and project-attached entries; manifest's external row
edit-pencil opens this dialog via forwardRef.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/server/routers/lunch.ts

@@ -153,7 +153,7 @@ export const lunchRouter = router({
         roleNote: z.string().max(500).optional(),
         dishId: z.string().nullable().optional(),
         allergens: allergens.optional(),
-        allergenOther: z.string().max(500).optional(),
+        allergenOther: z.string().max(500).nullable().optional(),
       }),
     )
     .mutation(async ({ ctx, input }) => {