refactor(validations): split lib/validations.ts into a barrel'd folder (slice 1)

1141-line lib/validations.ts → lib/validations/<feature>.ts + primitives.ts +
an index.ts barrel. '@/lib/validations' now resolves to the barrel, so all 40
importers are untouched. Every one of the 143 exports is preserved verbatim
(verified by symbol-diff); schemas moved unchanged. tsc 0, 635 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/validations/presence.ts

@@ -0,0 +1,10 @@
+import { z } from 'zod'
+
+export const checkInSchema = z.object({
+  asHost: z.boolean().optional().default(false),
+  note: z.string().max(500).optional().nullable(),
+})
+
+export const checkOutSchema = z.object({
+  note: z.string().max(500).optional().nullable(),
+})