WIP: 인스트루먼트 UI 시도 (DS 컴포넌트 + CRT 셰이더)

- DS 컴포넌트: CrtDisplay, InstrumentPanel, Led, PhysicalButton, MetalCard, PhosphorText
- Dashboard: CRT WebGL 셰이더 + 물리 버튼 + LED 클러스터
- 사이드바: 72px 미니 네비게이션
- 문제: SSOT 위반(매직넘버 41곳), 시안 A 정체성 부족, 모달/팝업 방치
- 다음: 디자인 근본 재설계 필요

src/renderer/components/ds/PhysicalButton.tsx

@@ -0,0 +1,43 @@
+// src/renderer/components/ds/PhysicalButton.tsx
+// 시안 A: 물리 버튼 — 돌출 그림자, 눌림 피드백, 선택 상태
+
+import { Button, type ButtonProps } from '@mui/material'
+
+interface PhysicalButtonProps extends Omit<ButtonProps, 'variant'> {
+  selected?: boolean
+}
+
+export function PhysicalButton({ selected = false, sx, ...props }: PhysicalButtonProps): React.ReactElement {
+  return (
+    <Button
+      {...props}
+      sx={{
+        height: 44,
+        bgcolor: selected ? '#1a1a1c' : '#242528',
+        border: 'none',
+        borderRadius: '6px',
+        color: selected ? '#f25b29' : '#77797c',
+        fontFamily: 'ui-monospace, SFMono-Regular, Menlo, Consolas, monospace',
+        fontSize: '12px',
+        fontWeight: 600,
+        cursor: 'pointer',
+        boxShadow: selected
+          ? 'inset 0 2px 6px rgba(0,0,0,0.8), inset 0 0 0 1px #000'
+          : '0 3px 6px rgba(0,0,0,0.4), inset 0 1px 1px rgba(255,255,255,0.1), inset 0 -1px 2px rgba(0,0,0,0.2)',
+        transform: selected ? 'translateY(1px)' : 'none',
+        transition: 'all 0.05s linear',
+        '&:active': {
+          transform: 'translateY(2px)',
+          boxShadow: '0 1px 2px rgba(0,0,0,0.4), inset 0 2px 4px rgba(0,0,0,0.3)',
+        },
+        '&:hover': {
+          bgcolor: selected ? '#1a1a1c' : '#2a2b2e',
+        },
+        textTransform: 'uppercase',
+        letterSpacing: '0.5px',
+        minWidth: 0,
+        ...sx,
+      }}
+    />
+  )
+}