refactor: 主入口 main.py 上移到 source/，端口重排为 9008/9007/9006

- main.py: source/openapi/main.py -> source/main.py
- 端口: 聚合层 9888->9008, pixiv 后端 9088->9007, bilibili 后端 19990->9006
- nginx/openapi.rrrosmontis.icu.conf: 三处 proxy_pass 指向 127.0.0.1:9008
- systemd/openapi.service: WorkingDirectory/ExecStart 同步为 source/

source/main.py

@@ -0,0 +1,55 @@
+from aiohttp import web, ClientSession, ClientTimeout
+
+
+PIXIV_BACKEND = "http://127.0.0.1:9088"
+BILIBILI_BACKEND = "http://127.0.0.1:19990"
+
+
+async def handle_pixiv(request):
+    pid = request.query.get("id", "")
+    if not pid:
+        return web.json_response({"error": "missing id parameter"}, status=400)
+    target = f"{PIXIV_BACKEND}/{pid}"
+    return await proxy(request, target)
+
+
+async def handle_bilibili(request):
+    qs = request.query_string
+    target = f"{BILIBILI_BACKEND}/bilibili/get_video"
+    if qs:
+        target += "?" + qs
+    return await proxy(request, target)
+
+
+async def proxy(request, target):
+    timeout = ClientTimeout(total=300)
+    async with ClientSession(timeout=timeout) as session:
+        try:
+            async with session.get(target) as resp:
+                body = await resp.read()
+                headers = {}
+                for key in ("Content-Type", "Content-Disposition", "Cache-Control"):
+                    if key in resp.headers:
+                        headers[key] = resp.headers[key]
+                return web.Response(
+                    body=body,
+                    status=resp.status,
+                    headers=headers,
+                )
+        except Exception as e:
+            return web.json_response(
+                {"error": "backend unreachable", "detail": str(e)}, status=502
+            )
+
+
+async def handle_root(request):
+    raise web.HTTPFound("https://rrrosmontis.icu/articles/index.html?id=00003")
+
+
+app = web.Application()
+app.router.add_get("/", handle_root)
+app.router.add_get("/pixiv/get_image", handle_pixiv)
+app.router.add_get("/bilibili/get_video", handle_bilibili)
+
+if __name__ == "__main__":
+    web.run_app(app, host="127.0.0.1", port=9888)