Enforce Go style rules across codebase

Apply five style rules: convert iota string enums to typed
string constants, replace errors.As with errors.AsType,
merge three-group imports into two groups, fix multiline
parameter/argument formatting, and replace fmt.Sprintf URL
construction with net/url.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/server/api/mcp/v1/middleware.go

@@ -15,9 +15,8 @@
 package mcp_v1
 
 import (
-	"net/http"
-
 	"errors"
+	"net/http"
 
 	"go.gearno.de/kit/httpserver"
 	"go.gearno.de/kit/log"