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/payments.ts

@@ -0,0 +1,14 @@
+import { z } from 'zod'
+import { flexibleDateTime } from './primitives'
+
+export const logCashPaymentSchema = z.object({
+  amount: z.number().positive('Amount must be positive'),
+  from_note: z.string().min(1, 'Payer note is required').max(500),
+  member_id: z.string().uuid('Invalid member ID').optional().nullable(),
+  transaction_date: flexibleDateTime().optional(),
+})
+
+export const linkPaymentSchema = z.object({
+  paymentId: z.string().uuid('Invalid payment ID'),
+  memberId: z.string().uuid('Invalid member ID'),
+})