refactor: split config into remotes/virtuals/locals sections (#31)

Repository types now live under dedicated top-level keys instead of a
shared remotes: block distinguished by a type field:

  remotes:   caching proxy remotes (no type field needed)
  virtuals:  virtual merged-index repositories
  locals:    local upload repositories

Routes for local repos move from /api/v1/remote/ to /api/v1/local/.
config.py gains get_virtual_config() and get_local_config() lookups.
Root endpoint now reports all three sections. Drop root conf.d/ (was
an exact duplicate of examples/conf.d-method/).

Reviewed-on: #31

src/artifactapi/artifact/virtual.py

@@ -147,11 +147,9 @@ _HANDLERS: dict[str, _VirtualHandler] = {
 
 
 async def handle(request: Request, virtual_name: str, path: str, storage, cache, config) -> Response:
-    virtual_cfg = config.get_remote_config(virtual_name)
+    virtual_cfg = config.get_virtual_config(virtual_name)
     if not virtual_cfg:
         raise HTTPException(status_code=404, detail=f"Virtual repository '{virtual_name}' not configured")
-    if virtual_cfg.get("type") != "virtual":
-        raise HTTPException(status_code=400, detail=f"'{virtual_name}' is not a virtual repository")
 
     package = virtual_cfg.get("package")
     handler = _HANDLERS.get(package)