chore(forms): remove unused vee-validate; formalize ref+validators+Zod as canonical pattern

Strict-regex sweep of apps/app/src/ confirms zero VeeValidate usage:
no `from 'vee-validate'` imports, no <Field|Form|ErrorMessage>,
no defineRule(), no useForm(). The 15 prior fuzzy matches were
false positives where /useForm/ matched useFormDraft/useFormSteps/
useFormSchemas/useFormFailures.

Changes:
- Remove `vee-validate` and `@vee-validate/zod` from apps/app/package.json
- Regenerate pnpm-lock.yaml (no other deps shifted)
- CLAUDE.md "Forms": replace VeeValidate prescription with the actual
  ref + @core/utils/validators + Zod-payload-schema pattern that the
  codebase already uses everywhere
- VUEXY_COMPONENTS.md: correct the stale "Registration uses VeeValidate"
  claim (the page actually uses useFormDraft + validators); update the
  "Form validation" reference row
- BACKLOG.md: close VEE-001 with the audit trail

All 319 existing tests still pass; vue-tsc clean.

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

CLAUDE.md

@@ -236,10 +236,24 @@ you are using available components rather than building custom ones.
 
 ### Forms
 
-- VeeValidate for form state + Zod for schema validation — always together
-- Zod schemas must mirror the backend Form Request rules (field names, required/optional, types)
+Canonical form pattern (used everywhere in the SPA):
+
+- `ref({ field: ... })` for form state
+- `VForm` ref + per-field rules drawn from `@core/utils/validators`
+  (`requiredValidator`, `emailValidator`, etc.)
+- A separate `errors: Ref<Record<string, string>>` for server-validation
+  feedback (mapped from 422 responses)
+- **Zod** for runtime validation of API payloads/responses (in
+  `apps/app/src/schemas/*.ts`) — Zod schemas mirror backend Form Requests
+  (field names, required/optional, types) and are the canonical contract
 - No inline validation logic in components
 
+VeeValidate is **NOT** the form library here. It was previously listed
+but never actually adopted in any page; it was removed in commit
+`<sha>` (Session 4 follow-up). Reference forms: `apps/app/src/components/sections/CreateShiftDialog.vue`,
+`apps/app/src/components/timetable/AddPerformanceDialog.vue`,
+`apps/app/src/pages/register/[public_token].vue`.
+
 ### Naming
 
 - DB columns: `snake_case`