feat(fsd): 허브·스페이스 중심 UI 목업 구조로 재편

맥락:

- 기존 라우트/컴포넌트 구조를 FSD 기준으로 정리하고, /app 허브와 /space 집중 화면 중심의 목업 흐름을 구성하기 위해

변경사항:

- App Router 구조를 /landing, /app, /space, /stats, /settings 중심으로 재배치

- entities/session/room/user 더미 데이터와 타입 정의 추가

- features(커스텀 입장, 룸 선택, 체크인, 리액션, 30초 리스타트 등) 단위로 로직 분리

- widgets(허브, 룸 갤러리, 타이머 HUD, 툴 도크 등) 조합형 UI 추가

- shared 공용 UI(Button/Chip/Modal/Toast 등) 및 유틸(cn/useReducedMotion) 정비

- 로그인 후 이동 경로를 /dashboard 에서 /app 으로 변경

- README를 현재 프로젝트 구조/라우트/구현 범위 기준으로 갱신

검증:

- npx tsc --noEmit

세션-상태: 허브·스페이스 목업이 FSD 레이어로 동작 가능하도록 정리됨

세션-다음: /space 상단 및 도크의 인원 수 카피를 분위기형 카피로 후속 정리

세션-리스크: build는 네트워크 환경에서 Google Fonts fetch 실패 가능

src/widgets/app-hub/ui/AppHubWidget.tsx

@@ -0,0 +1,147 @@
+'use client';
+
+import { useState } from 'react';
+import { useRouter } from 'next/navigation';
+import { getRoomBackgroundStyle, ROOM_THEMES } from '@/entities/room';
+import {
+  GOAL_CHIPS,
+  SOUND_PRESETS,
+  TIMER_PRESETS,
+  TODAY_ONE_LINER,
+  type GoalChip,
+} from '@/entities/session';
+import { MOCK_VIEWER } from '@/entities/user';
+import { type CustomEntrySelection } from '@/features/custom-entry-modal';
+import { useRoomSelection } from '@/features/room-select';
+import { useToast } from '@/shared/ui';
+import { AppTopBar } from '@/widgets/app-top-bar/ui/AppTopBar';
+import { CustomEntryWidget } from '@/widgets/custom-entry-widget/ui/CustomEntryWidget';
+import { RoomsGalleryWidget } from '@/widgets/rooms-gallery-widget/ui/RoomsGalleryWidget';
+import { StartRitualWidget } from '@/widgets/start-ritual-widget/ui/StartRitualWidget';
+
+const buildSpaceQuery = (
+  roomId: string,
+  goalInput: string,
+  soundPresetId: string,
+  timerLabel: string,
+) => {
+  const params = new URLSearchParams({
+    room: roomId,
+    sound: soundPresetId,
+    timer: timerLabel,
+  });
+
+  const normalizedGoal = goalInput.trim();
+
+  if (normalizedGoal) {
+    params.set('goal', normalizedGoal);
+  }
+
+  return params.toString();
+};
+
+export const AppHubWidget = () => {
+  const router = useRouter();
+  const { pushToast } = useToast();
+  const { selectedRoom, selectedRoomId, selectRoom } = useRoomSelection();
+
+  const [goalInput, setGoalInput] = useState('');
+  const [selectedGoalId, setSelectedGoalId] = useState<string | null>(null);
+  const [isCustomEntryOpen, setCustomEntryOpen] = useState(false);
+
+  const enterSpace = (soundPresetId: string, timerLabel: string) => {
+    const query = buildSpaceQuery(
+      selectedRoomId,
+      goalInput,
+      soundPresetId,
+      timerLabel,
+    );
+
+    router.push(`/space?${query}`);
+  };
+
+  const handleGoalChipSelect = (chip: GoalChip) => {
+    setSelectedGoalId(chip.id);
+    setGoalInput(chip.label);
+  };
+
+  const handleGoalInputChange = (value: string) => {
+    setGoalInput(value);
+
+    if (selectedGoalId && value.trim() === '') {
+      setSelectedGoalId(null);
+    }
+  };
+
+  const handleQuickEnter = () => {
+    enterSpace(SOUND_PRESETS[0].id, TIMER_PRESETS[0].label);
+  };
+
+  const handleCustomEnter = (selection: CustomEntrySelection) => {
+    setCustomEntryOpen(false);
+    enterSpace(selection.soundId, selection.timerLabel);
+  };
+
+  const handleLogout = () => {
+    pushToast({
+      title: '로그아웃은 목업에서만 동작해요',
+      description: '실제 인증 로직은 연결하지 않았습니다.',
+    });
+  };
+
+  return (
+    <div className="relative min-h-screen overflow-hidden text-white">
+      <div
+        aria-hidden
+        className="absolute inset-0"
+        style={getRoomBackgroundStyle(selectedRoom)}
+      />
+      <div aria-hidden className="absolute inset-0 bg-slate-950/60" />
+      <div
+        aria-hidden
+        className="absolute inset-0 opacity-40"
+        style={{
+          backgroundImage:
+            "url('/textures/grain.png'), repeating-linear-gradient(0deg, rgba(255,255,255,0.05) 0 1px, transparent 1px 2px)",
+          mixBlendMode: 'soft-light',
+        }}
+      />
+
+      <div className="relative z-10 flex min-h-screen flex-col">
+        <AppTopBar
+          user={MOCK_VIEWER}
+          oneLiner={TODAY_ONE_LINER}
+          onLogout={handleLogout}
+        />
+
+        <main className="mx-auto w-full max-w-7xl flex-1 px-4 pb-8 pt-6 sm:px-6 lg:px-8">
+          <div className="grid gap-6 xl:grid-cols-[minmax(320px,420px),1fr]">
+            <StartRitualWidget
+              goalInput={goalInput}
+              selectedGoalId={selectedGoalId}
+              goalChips={GOAL_CHIPS}
+              onGoalInputChange={handleGoalInputChange}
+              onGoalChipSelect={handleGoalChipSelect}
+              onQuickEnter={handleQuickEnter}
+              onOpenCustomEntry={() => setCustomEntryOpen(true)}
+            />
+
+            <RoomsGalleryWidget
+              rooms={ROOM_THEMES}
+              selectedRoomId={selectedRoomId}
+              onRoomSelect={selectRoom}
+            />
+          </div>
+        </main>
+      </div>
+
+      <CustomEntryWidget
+        isOpen={isCustomEntryOpen}
+        selectedRoomId={selectedRoomId}
+        onSelectRoom={selectRoom}
+        onClose={() => setCustomEntryOpen(false)}
+        onEnter={handleCustomEnter}
+      />
+    </div>
+  );
+};