feat: 테이블 테두리 및 라운드 제거, 검색 필터 제목 제거

- 모든 테이블 컴포넌트의 외곽 테두리(border) 제거
- 테이블 컨테이너의 라운드(rounded-lg) 제거
- 테이블 행 구분선(border-b)은 유지하여 데이터 구분
- FlowWidget과 TableListComponent에 동일한 스타일 적용
- 검색 필터 영역의 회색 배경(bg-muted/30) 제거
- 검색 필터 제목 제거
- AdvancedSearchFilters 컴포넌트의 '검색 필터' 제목 제거

frontend/components/admin/CompanyTable.tsx

@@ -49,10 +49,10 @@ export function CompanyTable({ companies, isLoading, onEdit, onDelete }: Company
     return (
       <>
         {/* 데스크톱 테이블 스켈레톤 */}
-        <div className="hidden rounded-lg border bg-card shadow-sm lg:block">
+        <div className="hidden bg-card shadow-sm lg:block">
           <Table>
             <TableHeader>
-              <TableRow className="border-b bg-muted/50 hover:bg-muted/50">
+              <TableRow className="bg-muted/50 hover:bg-muted/50">
                 {COMPANY_TABLE_COLUMNS.map((column) => (
                   <TableHead key={column.key} className="h-12 text-sm font-semibold">
                     {column.label}
@@ -64,7 +64,7 @@ export function CompanyTable({ companies, isLoading, onEdit, onDelete }: Company
             </TableHeader>
             <TableBody>
               {Array.from({ length: 10 }).map((_, index) => (
-                <TableRow key={index} className="border-b">
+                <TableRow key={index}>
                   <TableCell className="h-16">
                     <div className="h-4 animate-pulse rounded bg-muted"></div>
                   </TableCell>
@@ -117,7 +117,7 @@ export function CompanyTable({ companies, isLoading, onEdit, onDelete }: Company
   // 데이터가 없을 때
   if (companies.length === 0) {
     return (
-      <div className="flex h-64 flex-col items-center justify-center rounded-lg border bg-card shadow-sm">
+      <div className="flex h-64 flex-col items-center justify-center bg-card shadow-sm">
         <div className="flex flex-col items-center gap-2 text-center">
           <p className="text-sm text-muted-foreground">등록된 회사가 없습니다.</p>
         </div>
@@ -129,10 +129,10 @@ export function CompanyTable({ companies, isLoading, onEdit, onDelete }: Company
   return (
     <>
       {/* 데스크톱 테이블 뷰 (lg 이상) */}
-      <div className="hidden rounded-lg border bg-card shadow-sm lg:block">
+      <div className="hidden bg-card shadow-sm lg:block">
         <Table>
           <TableHeader>
-            <TableRow className="border-b bg-muted/50 hover:bg-muted/50">
+            <TableRow className="bg-muted/50 hover:bg-muted/50">
               {COMPANY_TABLE_COLUMNS.map((column) => (
                 <TableHead key={column.key} className="h-12 text-sm font-semibold">
                   {column.label}
@@ -144,7 +144,7 @@ export function CompanyTable({ companies, isLoading, onEdit, onDelete }: Company
           </TableHeader>
           <TableBody>
             {companies.map((company) => (
-              <TableRow key={company.regdate + company.company_code} className="border-b transition-colors hover:bg-muted/50">
+              <TableRow key={company.regdate + company.company_code} className="transition-colors hover:bg-muted/50">
                 <TableCell className="h-16 font-mono text-sm">{company.company_code}</TableCell>
                 <TableCell className="h-16 text-sm font-medium">{company.company_name}</TableCell>
                 <TableCell className="h-16 text-sm">{company.writer}</TableCell>