Revert feature-folder migration; keep classic src/components + src/hooks layout

Decision: the src/features/<feature>/ layout introduced as proposal #3
(pilot on doorbell in 8ec9d27) is not the convention the team wants. The
existing src/components/<area>/ + src/hooks/<area>/ split is the one
that stays.

What's reverted
- src/features/doorbell/ is removed entirely. The doorbell view and the
  two hooks move back under the classic paths:
    src/features/doorbell/views/DoorbellWidgetView.tsx
      -> src/components/room/widgets/doorbell/DoorbellWidgetView.tsx
    src/features/doorbell/hooks/useDoorbellState.ts
      -> src/hooks/rooms/widgets/useDoorbellState.ts
    src/features/doorbell/hooks/useDoorbellActions.ts
      -> src/hooks/rooms/widgets/useDoorbellActions.ts
- The compat shims that lived in those classic paths are dropped now
  that the real files are back.
- src/hooks/rooms/widgets/index.ts adds the two new hooks alongside the
  existing useDoorbellWidget shim (kept as a deprecated wrapper so any
  external consumer importing the old shape via the barrel keeps
  working).

What's preserved
- The split between data and actions (proposal #4) — useDoorbellState
  and useDoorbellActions remain two separate hooks. This was the actual
  improvement, and it's independent of where the files sit.
- The bug fixes from 8ec9d27 (close button race, optimistic-remove
  rollback) — both still present, just in the new path.
- src/state/createNitroStore.ts and src/api/nitro-query/createNitroQuery.ts
  are left where they are. They aren't feature folders; they're
  cross-cutting framework code (Zustand skeleton, React Query adapter
  prototype) that any feature can consume.

Doc
- docs/ARCHITECTURE.md section #3 is rewritten to record the decision
  rather than recommend the layout. It now describes the convention to
  follow:
    * views under src/components/<area>/<feature>/
    * hooks under src/hooks/<area>/<feature?>/ (siblings, not subfolders
      per widget)
    * sibling .types/.constants/.helpers files for view-specific code
      (e.g. WiredCreatorTools.*.ts)
- "What's already in place" and "Recently fixed" sections updated to
  point at the new paths.
- "How to pick the next refactor PR" no longer mentions feature-folder
  migration as an option.

Note: the five extra feature folders started this session (reconnect,
nitropedia, ads, hc-center, campaign) were never committed; they only
existed in the working tree and have been restored from HEAD.

Verification
- find src/features -type f -> 0 (directory removed).
- npx tsc --noEmit on all touched files: clean (only the project-wide
  pre-existing TS2307 about @nitrots/nitro-renderer not installed
  locally remains, same as before).
- npx eslint on all touched files: 0 errors, 0 warnings.

https://claude.ai/code/session_01GrR87LAqnAEyKG2ZbmQt5Q

src/hooks/rooms/widgets/index.ts

@@ -3,6 +3,8 @@ export * from './useAvatarInfoWidget';
 export * from './useChatCommandSelector';
 export * from './useChatInputWidget';
 export * from './useChatWidget';
+export * from './useDoorbellActions';
+export * from './useDoorbellState';
 export * from './useDoorbellWidget';
 export * from './useFilterWordsWidget';
 export * from './useFriendRequestWidget';

src/hooks/rooms/widgets/useDoorbellActions.ts

@@ -0,0 +1,13 @@
+import { GetRoomSession } from '../../../api';
+
+/**
+ * Imperative actions for the doorbell. Stateless on purpose — split from
+ * useDoorbellState so components that only need to dispatch an answer
+ * don't subscribe to the events.
+ */
+export const useDoorbellActions = () => ({
+    answer: (userName: string, flag: boolean): void =>
+    {
+        GetRoomSession()?.sendDoorbellApprovalMessage(userName, flag);
+    }
+});

src/hooks/rooms/widgets/useDoorbellState.ts

@@ -0,0 +1,44 @@
+import { RoomSessionDoorbellEvent } from '@nitrots/nitro-renderer';
+import { useCallback, useLayoutEffect, useRef, useState } from 'react';
+import { useNitroEvent } from '../../events';
+
+/**
+ * Reduces the three doorbell events (DOORBELL, RSDE_ACCEPTED, RSDE_REJECTED)
+ * into a single users array. Data-only hook split — actions live in
+ * useDoorbellActions.
+ */
+export const useDoorbellState = (): readonly string[] =>
+{
+    const [ users, setUsers ] = useState<string[]>([]);
+
+    const usersRef = useRef(users);
+
+    useLayoutEffect(() =>
+    {
+        usersRef.current = users;
+    });
+
+    const handleAdd = useCallback((event: RoomSessionDoorbellEvent) =>
+    {
+        if(usersRef.current.indexOf(event.userName) >= 0) return;
+
+        setUsers([ ...usersRef.current, event.userName ]);
+    }, []);
+
+    const handleRemove = useCallback((event: RoomSessionDoorbellEvent) =>
+    {
+        const index = usersRef.current.indexOf(event.userName);
+
+        if(index === -1) return;
+
+        const next = [ ...usersRef.current ];
+        next.splice(index, 1);
+        setUsers(next);
+    }, []);
+
+    useNitroEvent<RoomSessionDoorbellEvent>(RoomSessionDoorbellEvent.DOORBELL, handleAdd);
+    useNitroEvent<RoomSessionDoorbellEvent>(RoomSessionDoorbellEvent.RSDE_ACCEPTED, handleRemove);
+    useNitroEvent<RoomSessionDoorbellEvent>(RoomSessionDoorbellEvent.RSDE_REJECTED, handleRemove);
+
+    return users;
+};

src/hooks/rooms/widgets/useDoorbellWidget.ts

@@ -1,9 +1,10 @@
-import { useDoorbellActions, useDoorbellState } from '../../../features/doorbell';
+import { useDoorbellActions } from './useDoorbellActions';
+import { useDoorbellState } from './useDoorbellState';
 
 /**
- * @deprecated Use `useDoorbellState` and `useDoorbellActions` from
- * `src/features/doorbell` directly. This shim is kept so existing
- * imports via the `hooks` barrel keep working.
+ * @deprecated Use `useDoorbellState` and `useDoorbellActions` directly.
+ * This shim preserves the old `{ users, answer }` shape so existing
+ * imports keep working.
  */
 export const useDoorbellWidget = () =>
 {