fix: add missing checks to several API and web handlers (#39501) (#39507)

Backport #39501 by @silverwind

Several handlers skipped checks that their sibling routes or settings
already enforce. This brings them in line.

- Push mirror API honors `DISABLE_NEW_PUSH` and checks the caller's
permission
- Media API serves small files with the usual content headers
- Issue attachment API ignores comment attachments
- Push-to-create respects `FORCE_PRIVATE`
- Profile feeds and follow actions respect `ENABLE_FEED` and owner
visibility
- Tag delete route refuses release tags
- Refresh token grant only accepts refresh tokens
- Gitea migrations bound the source's page size

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: bircni <bircni@icloud.com>

routers/api/v1/repo/file.go

@@ -162,7 +162,7 @@ func GetRawFileOrLFS(ctx *context.APIContext) {
 
 	// if it's not a pointer, just serve the data directly
 	if !pointer.IsValid() {
-		_, _ = ctx.Resp.Write(lfsPointerBuf)
+		httplib.ServeUserContentByReader(ctx.Req, ctx.Resp, int64(len(lfsPointerBuf)), bytes.NewReader(lfsPointerBuf), httplib.ServeHeaderOptions{Filename: blob.Name()})
 		return
 	}
 
@@ -171,7 +171,7 @@ func GetRawFileOrLFS(ctx *context.APIContext) {
 
 	// If there isn't one, just serve the data directly
 	if errors.Is(err, git_model.ErrLFSObjectNotExist) {
-		_, _ = ctx.Resp.Write(lfsPointerBuf)
+		httplib.ServeUserContentByReader(ctx.Req, ctx.Resp, int64(len(lfsPointerBuf)), bytes.NewReader(lfsPointerBuf), httplib.ServeHeaderOptions{Filename: blob.Name()})
 		return
 	} else if err != nil {
 		ctx.APIErrorInternal(err)
@@ -198,7 +198,7 @@ func GetRawFileOrLFS(ctx *context.APIContext) {
 		return
 	}
 	defer lfsDataFile.Close()
-	httplib.ServeUserContentByFile(ctx.Base.Req, ctx.Base.Resp, lfsDataFile, httplib.ServeHeaderOptions{Filename: ctx.Repo.TreePath})
+	httplib.ServeUserContentByFile(ctx.Base.Req, ctx.Base.Resp, lfsDataFile, httplib.ServeHeaderOptions{Filename: blob.Name()})
 }
 
 func getBlobForEntry(ctx *context.APIContext) (blob *git.Blob, entry *git.TreeEntry, lastModified *time.Time) {