chore: enable forcetypeassert linter, fix issues (#38804)

Enable [`forcetypeassert`](https://github.com/gostaticanalysis/forcetypeassert)
linter to prevent unchecked type assertions. ~650 issues fixed, most
fixes were clean, some use `setting.PanicInDevOrTesting`.

The only behaviour changes are where code would previously send a 500 error
or panic, a 4xx error is now emitted.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/markup/markdown/transform_blockquote.go

@@ -18,7 +18,7 @@ import (
 // renderAttention renders a quote marked with i.e. "> **Note**" or "> [!Warning]" with a corresponding svg
 func (r *HTMLRenderer) renderAttention(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if entering {
-		n := node.(*Attention)
+		n := node.(*Attention) //nolint:forcetypeassert // registered for KindAttention only
 		var octiconName string
 		switch n.AttentionType {
 		case "tip":