Fix CodeQL code scanning alerts (#36858)

Fixes 10 CodeQL code scanning alerts:

- Change `NewPagination`/`SetLinkHeader` to accept `int64` for total
count, clamping internally to fix incorrect-integer-conversion alerts
([#110](https://github.com/go-gitea/gitea/security/code-scanning/110),
[#114](https://github.com/go-gitea/gitea/security/code-scanning/114),
[#115](https://github.com/go-gitea/gitea/security/code-scanning/115),
[#116](https://github.com/go-gitea/gitea/security/code-scanning/116))
- Use `strconv.Atoi()` in `htmlrenderer.go` to avoid int64 intermediate
([#105](https://github.com/go-gitea/gitea/security/code-scanning/105),
[#106](https://github.com/go-gitea/gitea/security/code-scanning/106))
- Clamp regex match indices in `escape_stream.go` to fix
allocation-size-overflow
([#161](https://github.com/go-gitea/gitea/security/code-scanning/161),
[#162](https://github.com/go-gitea/gitea/security/code-scanning/162),
[#163](https://github.com/go-gitea/gitea/security/code-scanning/163))
- Cap slice pre-allocation in `GetIssueDependencies`
([#181](https://github.com/go-gitea/gitea/security/code-scanning/181))

---------

Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/v1/repo/pull.go

@@ -154,7 +154,7 @@ func ListPullRequests(ctx *context.APIContext) {
 		return
 	}
 
-	ctx.SetLinkHeader(int(maxResults), listOptions.PageSize)
+	ctx.SetLinkHeader(maxResults, listOptions.PageSize)
 	ctx.SetTotalCountHeader(maxResults)
 	ctx.JSON(http.StatusOK, &apiPrs)
 }
@@ -1449,7 +1449,7 @@ func GetPullRequestCommits(ctx *context.APIContext) {
 		apiCommits = append(apiCommits, apiCommit)
 	}
 
-	ctx.SetLinkHeader(totalNumberOfCommits, listOptions.PageSize)
+	ctx.SetLinkHeader(int64(totalNumberOfCommits), listOptions.PageSize)
 	ctx.SetTotalCountHeader(int64(totalNumberOfCommits))
 
 	ctx.RespHeader().Set("X-Page", strconv.Itoa(listOptions.Page))
@@ -1591,7 +1591,7 @@ func GetPullRequestFiles(ctx *context.APIContext) {
 		apiFiles = append(apiFiles, convert.ToChangedFile(diff.Files[i], pr.BaseRepo, endCommitID))
 	}
 
-	ctx.SetLinkHeader(totalNumberOfFiles, listOptions.PageSize)
+	ctx.SetLinkHeader(int64(totalNumberOfFiles), listOptions.PageSize)
 	ctx.SetTotalCountHeader(int64(totalNumberOfFiles))
 
 	ctx.RespHeader().Set("X-Page", strconv.Itoa(listOptions.Page))