fix(frontend): Select 접근성 — aria-label 필수 + 네이티브 <select> 보완

이슈: "Select element must have an accessible name" — 스크린 리더가 용도를
인지할 수 없어 WCAG 2.1 Level A 위반.

수정:
- Select 공통 컴포넌트 타입을 union으로 강제
  - aria-label | aria-labelledby | title 중 하나는 TypeScript 컴파일 타임에 필수
  - 누락 시 tsc 단계에서 즉시 실패 → 회귀 방지
- 네이티브 <select> 5곳 aria-label 추가:
  - admin/SystemConfig: 대분류 필터
  - detection/RealVesselAnalysis: 해역 필터
  - detection/RealGearGroups: 그룹 유형 필터
  - detection/ChinaFishing: 관심영역 선택
  - detection/GearIdentification: SelectField에 label prop 추가
- 쇼케이스 FormSection Select 샘플에 aria-label 추가

이제 모든 Select 사용처가 접근 이름을 가지며,
향후 신규 Select 사용 시 tsc가 누락을 차단함.

frontend/src/design-system/sections/FormSection.tsx

@@ -63,7 +63,7 @@ export function FormSection() {
         {(['sm', 'md', 'lg'] as const).map((size) => (
           <Trk key={size} id={`TRK-FORM-select-${size}`} className="ds-sample">
             <label className="text-[10px] text-hint font-mono mb-1 block">size={size}</label>
-            <Select size={size} defaultValue="">
+            <Select aria-label={`쇼케이스 샘플 Select ${size}`} size={size} defaultValue="">
               <option value="">전체 선택</option>
               <option value="CRITICAL">CRITICAL</option>
               <option value="HIGH">HIGH</option>

frontend/src/features/admin/SystemConfig.tsx

@@ -232,6 +232,7 @@ export function SystemConfig() {
           <div className="flex items-center gap-1.5">
             <Filter className="w-3.5 h-3.5 text-hint" />
             <select
+              aria-label="대분류 필터"
               value={majorFilter}
               onChange={(e) => { setMajorFilter(e.target.value); setPage(0); }}
               className="bg-surface-overlay border border-slate-700/50 rounded-lg px-3 py-2 text-[11px] text-label focus:outline-none focus:border-cyan-500/50"

frontend/src/features/detection/ChinaFishing.tsx

@@ -428,7 +428,7 @@ export function ChinaFishing() {
             <CardContent className="p-4">
               <div className="flex items-center justify-between mb-2">
                 <span className="text-sm font-bold text-heading">관심영역 안전도</span>
-                <select className="bg-secondary border border-slate-700/50 rounded px-2 py-0.5 text-[10px] text-label focus:outline-none">
+                <select aria-label="관심영역 선택" className="bg-secondary border border-slate-700/50 rounded px-2 py-0.5 text-[10px] text-label focus:outline-none">
                   <option>영역 A</option>
                   <option>영역 B</option>
                 </select>

frontend/src/features/detection/GearIdentification.tsx

@@ -470,13 +470,15 @@ function Toggle({ checked, onChange, label }: { checked: boolean; onChange: (v:
   );
 }
 
-function SelectField({ value, onChange, options }: {
+function SelectField({ label, value, onChange, options }: {
+  label: string;
   value: string;
   onChange: (v: string) => void;
   options: { value: string; label: string }[];
 }) {
   return (
     <select
+      aria-label={label}
       value={value}
       onChange={(e) => onChange(e.target.value)}
       className="w-full bg-surface-overlay border border-slate-700/50 rounded-md px-2.5 py-1.5 text-xs text-heading focus:border-blue-500/50 focus:outline-none"
@@ -692,7 +694,7 @@ export function GearIdentification() {
             <CardContent className="p-4 space-y-3">
               <SectionHeader icon={Anchor} title="어구 물리적 특성" color="#a855f7" />
               <FormField label="어구 유형 (추정)">
-                <SelectField value={input.gearCategory} onChange={(v) => update('gearCategory', v as GearType)} options={[
+                <SelectField label="어구 유형 (추정)" value={input.gearCategory} onChange={(v) => update('gearCategory', v as GearType)} options={[
                   { value: 'unknown', label: '미확인 / 모름' },
                   { value: 'trawl', label: '트롤 (저인망) — 끌고 다니는 어망' },
                   { value: 'gillnet', label: '자망 (유자망) — 세워놓는 어망' },
@@ -746,7 +748,7 @@ export function GearIdentification() {
                 </FormField>
               </div>
               <FormField label="궤적 패턴">
-                <SelectField value={input.trajectoryPattern} onChange={(v) => update('trajectoryPattern', v as GearInput['trajectoryPattern'])} options={[
+                <SelectField label="궤적 패턴" value={input.trajectoryPattern} onChange={(v) => update('trajectoryPattern', v as GearInput['trajectoryPattern'])} options={[
                   { value: 'unknown', label: '미확인' },
                   { value: 'lawnmowing', label: '지그재그 반복 (Lawn-mowing) → 트롤' },
                   { value: 'stationary', label: '정지/극저속 (Stationary) → 자망' },

frontend/src/features/detection/RealGearGroups.tsx

@@ -62,7 +62,7 @@ export function RealGearGroups() {
             </div>
           </div>
           <div className="flex items-center gap-2">
-            <select value={filterType} onChange={(e) => setFilterType(e.target.value)}
+            <select aria-label="그룹 유형 필터" value={filterType} onChange={(e) => setFilterType(e.target.value)}
                     className="bg-surface-overlay border border-border rounded px-2 py-1 text-[10px] text-heading">
               <option value="">전체</option>
               <option value="FLEET">FLEET</option>

frontend/src/features/detection/RealVesselAnalysis.tsx

@@ -85,7 +85,7 @@ export function RealVesselAnalysis({ mode, title, icon }: Props) {
             </div>
           </div>
           <div className="flex items-center gap-2">
-            <select value={zoneFilter} onChange={(e) => setZoneFilter(e.target.value)}
+            <select aria-label="해역 필터" value={zoneFilter} onChange={(e) => setZoneFilter(e.target.value)}
                     className="bg-surface-overlay border border-border rounded px-2 py-1 text-[10px] text-heading">
               <option value="">전체 해역</option>
               <option value="TERRITORIAL_SEA">영해</option>

frontend/src/shared/components/ui/select.tsx

@@ -2,12 +2,32 @@ import { forwardRef, type SelectHTMLAttributes } from 'react';
 import { inputVariants, type InputSize, type InputState } from '@lib/theme/variants';
 import { cn } from '@lib/utils/cn';
 
-export interface SelectProps extends Omit<SelectHTMLAttributes<HTMLSelectElement>, 'size'> {
+/**
+ * Select — 네이티브 select 래퍼.
+ *
+ * **접근성 정책 (타입으로 강제)**:
+ * 스크린 리더가 select의 용도를 읽을 수 있도록 아래 3개 중 하나는 필수:
+ *  - `aria-label`: 짧은 텍스트 라벨 (예: "등급 필터")
+ *  - `aria-labelledby`: 다른 요소의 ID 참조
+ *  - `title`: 툴팁 (접근 이름 폴백)
+ *
+ * 사용 예:
+ *   <Select aria-label="상태 필터" value={v} onChange={...}>...</Select>
+ *   <Select title="등급 필터" value={v} onChange={...}>...</Select>
+ */
+
+type BaseSelectProps = Omit<SelectHTMLAttributes<HTMLSelectElement>, 'size'> & {
   size?: InputSize;
   state?: InputState;
-}
+};
+
+type SelectWithAccessibleName =
+  | (BaseSelectProps & { 'aria-label': string })
+  | (BaseSelectProps & { 'aria-labelledby': string })
+  | (BaseSelectProps & { title: string });
+
+export type SelectProps = SelectWithAccessibleName;
 
-/** Select — Input과 동일한 스타일 토큰 공유 */
 export const Select = forwardRef<HTMLSelectElement, SelectProps>(
   ({ className, size, state, children, ...props }, ref) => {
     return (