feat: add NsesApi — REST CRUD endpoints for NSE script management

[t0kubetsu]

Problem

NSE scripts can only be managed through the /nsesview HTML form interface. There are no REST API endpoints for NSE scripts, making programmatic management (upload, update, delete) impossible without scraping HTML and CSRF tokens.

Proposed solution

Add a new NsesApi(BaseApi) class at /api/v1/nses with full CRUD:

Method	Path	Action
GET	/api/v1/nses/	list all NSE scripts ({id, name, hash})
POST	/api/v1/nses/	upload a new .nse file (multipart filebody); upserts on name collision
GET	/api/v1/nses/<pk>	read a single script by ID
PUT	/api/v1/nses/<pk>	update file content and/or rename in-place
DELETE	/api/v1/nses/<pk>	delete by ID

All endpoints use @protect() (JWT or session auth) and @safe.

The PUT endpoint:

• accepts an optional filebody multipart file and/or an optional name form field (at least one required)
• validates the .nse extension on upload
• rejects SHA-256 hash collisions with other records
• uses FileManager to replace the file on disk atomically

Motivation

External automation clients need a stable REST interface to manage deployed NSE scripts without recycling IDs or scraping HTML forms. An in-place PUT avoids the race-condition window between delete and re-create.