feat: 스니펫 공용화 — 서버 PostgreSQL 테이블 + API, 프론트는 브릿지 대신 HTTP

결정(9/21): 공용 하나, 개인 로컬 없음.
- backend apps/snippets: Snippet(name PK·desc·body·category) + SnippetUsage(사람별 count/last_used).
  GET/POST /api/v1/snippets, PUT/DELETE /snippets/{name}, POST /snippets/{name}/use — 옛 브릿지 5개와 1:1,
  이름 정규화·중복 409·빈 내용 400 규칙 동일. import_snippets 커맨드로 옛 snippets.db 적재. 테스트 3개
- frontend snippets.api.ts 만 HTTP 로 교체(훅·페이지·타입 무변경). 테스트 axios-mock-adapter 로
- ponytail: Tauri 로컬 SQLite 커맨드는 미사용 상태로 남김. 지울 때 Rust+브릿지 테스트 함께

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

5_django_backend/apps/snippets/views.py

@@ -0,0 +1,77 @@
+"""스니펫 API — 프론트 `features/snippets/api/snippets.api.ts` 5개 호출과 1:1. 옛 Tauri 브릿지 규칙 그대로.
+
+  GET    /api/v1/snippets              → Snippet[] (내 usage 합쳐서)
+  POST   /api/v1/snippets              {name,desc,body,category} → Snippet (이름 중복이면 409)
+  PUT    /api/v1/snippets/{name}       {desc,body,category} → Snippet
+  DELETE /api/v1/snippets/{name}       → {name}
+  POST   /api/v1/snippets/{name}/use   → {name, usageCount, lastUsed}
+"""
+
+from django.db import IntegrityError, transaction
+from django.shortcuts import get_object_or_404
+from django.utils import timezone
+from rest_framework.response import Response
+from rest_framework.views import APIView
+
+from common.envelope import CodedError
+
+from .models import Snippet, SnippetUsage
+
+
+def normalize_name(name: str) -> str:
+    return (name or "").strip().upper().replace(" ", "_")
+
+
+def _validate(body: dict, *, need_name: bool) -> dict:
+    name = normalize_name(body.get("name", ""))
+    if need_name and not name:
+        raise CodedError(400, "VALIDATION_ERROR", "이름을 입력해야 함")
+    if not (body.get("body") or "").strip():
+        raise CodedError(400, "VALIDATION_ERROR", "내용을 입력해야 함")
+    return {
+        "name": name,
+        "desc": body.get("desc") or "",
+        "body": body["body"],
+        "category": (body.get("category") or "").strip() or "코드",
+    }
+
+
+class SnippetListView(APIView):
+    def get(self, request):
+        usage = {u.snippet_id: u for u in SnippetUsage.objects.filter(user=request.user)}
+        return Response([s.as_dto(usage.get(s.name)) for s in Snippet.objects.all()])
+
+    def post(self, request):
+        d = _validate(request.data, need_name=True)
+        try:
+            with transaction.atomic():  # 중복 INSERT 실패가 바깥 트랜잭션을 깨지 않게(savepoint)
+                s = Snippet.objects.create(**d, created_by=request.user)
+        except IntegrityError:
+            raise CodedError(409, "CONFLICT", f"이미 있는 이름임: {d['name']}")
+        return Response(s.as_dto(), status=201)
+
+
+class SnippetDetailView(APIView):
+    def put(self, request, name: str):
+        s = get_object_or_404(Snippet, name=normalize_name(name))
+        d = _validate({**request.data, "name": s.name}, need_name=False)
+        s.desc, s.body, s.category = d["desc"], d["body"], d["category"]
+        s.save(update_fields=["desc", "body", "category", "updated_at"])
+        usage = SnippetUsage.objects.filter(snippet=s, user=request.user).first()
+        return Response(s.as_dto(usage))
+
+    def delete(self, request, name: str):
+        s = get_object_or_404(Snippet, name=normalize_name(name))
+        deleted = s.name  # delete() 가 pk 를 None 으로 지움
+        s.delete()
+        return Response({"name": deleted})
+
+
+class SnippetUseView(APIView):
+    def post(self, request, name: str):
+        s = get_object_or_404(Snippet, name=normalize_name(name))
+        u, _ = SnippetUsage.objects.get_or_create(snippet=s, user=request.user)
+        u.count += 1
+        u.last_used = timezone.now()
+        u.save(update_fields=["count", "last_used"])
+        return Response({"name": s.name, "usageCount": u.count, "lastUsed": int(u.last_used.timestamp())})