v1.0.0 배포 준비: CHANGELOG, LICENSE, 프로젝트 메타 파일 추가

- CHANGELOG.md: Phase 1~13 + 랜딩 페이지 전체 변경 이력
- LICENSE: MIT
- CONTRIBUTING.md: 개발 환경, 코드 표준, PR 프로세스
- SECURITY.md: 보안 정책, 취약점 보고 절차
- .editorconfig: 에디터 설정 통일 (indent, charset, eol)
- .nvmrc: Node.js 20
- .gitattributes: line ending 정규화, 바이너리 선언, linguist 설정
- .gitignore: site/dist, Python, Whisper 모델 등 누락 항목 추가

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 D3RO
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.