chore(deps): drop four dependencies nothing imports

react-hook-form, @hookform/resolvers, next-themes and @vitejs/plugin-react
have no import anywhere in src/, scripts/, tests/, e2e/ or the build and
test configs; knip only stayed quiet because each sat on its ignore list.
Forms keep a controlled draft and validate with the shared Zod schemas,
and the theme bootstrap is hand-written. The ignore entries, the comments
that still named the form library, and the guideline text go with them.

docs/ui-guidelines.md

@@ -132,7 +132,8 @@ helper text explaining why. Silent disabled buttons frustrate users.
 
 ### 2.2 Inputs and forms
 
-We use `react-hook-form` + Zod schemas from `src/lib/validations/`.
+Forms keep a controlled draft in component state and validate it with the
+Zod schemas from `src/lib/validations/`; the server's schema is the authority.
 Wrap inputs in `<label>` (visible) plus `aria-describedby` for helper text.
 
 - **Text / number / email**: `<Input>`. Always set `autocomplete`. See §4.4.
@@ -425,8 +426,7 @@ control. Behavior:
 
 ### 4.6 Server actions and mutations
 
-We use `react-hook-form` + TanStack Query mutations, never raw fetch
-calls in components. Every mutation:
+Mutations go through TanStack Query, never raw fetch calls in components. Every mutation:
 
 1. Optimistically updates the cache with a rollback handler.
 2. Toast on success ("Saved" — translated) and on error (with retry).