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/web/user/home.go

@@ -301,15 +301,15 @@ func Milestones(ctx *context.Context) {
 		return !showRepoIDs.Contains(v)
 	})
 
-	var pagerCount int
+	var pagerCount int64
 	if isShowClosed {
 		ctx.Data["State"] = "closed"
 		ctx.Data["Total"] = totalMilestoneStats.ClosedCount
-		pagerCount = int(milestoneStats.ClosedCount)
+		pagerCount = milestoneStats.ClosedCount
 	} else {
 		ctx.Data["State"] = "open"
 		ctx.Data["Total"] = totalMilestoneStats.OpenCount
-		pagerCount = int(milestoneStats.OpenCount)
+		pagerCount = milestoneStats.OpenCount
 	}
 
 	ctx.Data["Milestones"] = milestones
@@ -578,11 +578,11 @@ func buildIssueOverview(ctx *context.Context, unitType unit.Type) {
 	}
 
 	// Will be posted to ctx.Data.
-	var shownIssues int
+	var shownIssues int64
 	if !isShowClosed {
-		shownIssues = int(issueStats.OpenCount)
+		shownIssues = issueStats.OpenCount
 	} else {
-		shownIssues = int(issueStats.ClosedCount)
+		shownIssues = issueStats.ClosedCount
 	}
 
 	ctx.Data["IsShowClosed"] = isShowClosed