refactor: use named Permission field in Repository struct instead of anonymous embedding (#37441)

The `Repository` struct in `services/context/repo.go` embedded
`access_model.Permission` anonymously, causing all permission methods to
be promoted directly onto `Repository`. This made it unclear at call
sites whether a method belonged to `Repository` itself or to its
embedded `Permission`.

### Changes

- **`services/context/repo.go`**: Replace anonymous
`access_model.Permission` with named field `Permission
access_model.Permission`
- **49 files** updated to route permission method calls through the
named field:

```go
// Before
ctx.Repo.IsAdmin()
ctx.Repo.CanWrite(unit.TypeCode)
ctx.Repo.CanReadIssuesOrPulls(isPull)
slices.ContainsFunc(unitTypes, ctx.Repo.CanWrite)

// After
ctx.Repo.Permission.IsAdmin()
ctx.Repo.Permission.CanWrite(unit.TypeCode)
ctx.Repo.Permission.CanReadIssuesOrPulls(isPull)
slices.ContainsFunc(unitTypes, ctx.Repo.Permission.CanWrite)
```

Methods defined directly on `*Repository` (`CanWriteToBranch`,
`CanCreateBranch`, etc.) are unchanged.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wxiaoguang <2114189+wxiaoguang@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Nicolas <bircni@icloud.com>

routers/web/repo/activity.go

@@ -48,7 +48,7 @@ func Activity(ctx *context.Context) {
 	ctx.Data["Period"] = period
 	ctx.Data["PeriodText"] = ctx.Tr("repo.activity.period." + period)
 
-	canReadCode := ctx.Repo.CanRead(unit.TypeCode)
+	canReadCode := ctx.Repo.Permission.CanRead(unit.TypeCode)
 	if canReadCode {
 		// GetActivityStats needs to read the default branch to get some information
 		branchExist, _ := git_model.IsBranchExist(ctx, ctx.Repo.Repository.ID, ctx.Repo.Repository.DefaultBranch)
@@ -62,9 +62,9 @@ func Activity(ctx *context.Context) {
 	var err error
 	// TODO: refactor these arguments to a struct
 	ctx.Data["Activity"], err = activities_model.GetActivityStats(ctx, ctx.Repo.Repository, timeFrom,
-		ctx.Repo.CanRead(unit.TypeReleases),
-		ctx.Repo.CanRead(unit.TypeIssues),
-		ctx.Repo.CanRead(unit.TypePullRequests),
+		ctx.Repo.Permission.CanRead(unit.TypeReleases),
+		ctx.Repo.Permission.CanRead(unit.TypeIssues),
+		ctx.Repo.Permission.CanRead(unit.TypePullRequests),
 		canReadCode,
 	)
 	if err != nil {