refactor: add settings, transport and alias packages (#1122)

Part 1/5 of the tea 1.0 rewrite.

**Stack** (split from #1121; each PR targets `main` and builds, tests and lints on its own — the shipped CLI only changes in part 5):

1. #1122 Toolchain and foundation packages ← this PR
2. #1123 Credentials and Git
3. #1124 Terminal
4. #1125 Services
5. #1126 CLI wiring, docs, removal of the old tree

## Changes

- **build:** require Go 1.27; bump gofumpt and golangci-lint to releases that can read Go 1.27 export data (own commit).
- `internal/clierr`: typed errors and executable exit codes.
- `internal/version`: build version and tags.
- `internal/filelock`: moved unchanged from `modules/filelock`.
- `internal/aliases`: user-defined command aliases.
- `internal/transport`: the HTTP client the Gitea SDK runs on (part 4): token, Sudo and SSH-signature auth, retries for safe reads, connect/TLS/response-header timeouts, typed API errors that keep Gitea's message, and a redacted request log for `--debug`; plus raw requests for `tea api`, signed downloads that follow object-storage redirects, and log streaming.
- `internal/settings`: split `config.yml` / `hosts.yml` with locked transactions, plus remote URL parsing.

Nothing imports these packages yet.

Note: `flake.nix` now asks for `go_1_27`; the pinned nixpkgs in `flake.lock` predates Go 1.27 and still needs a `nix flake update nixpkgs`.
Reviewed-on: https://gitea.com/gitea/tea/pulls/1122
Reviewed-by: TheFox0x7 <95654+thefox0x7@noreply.gitea.com>

modules/interact/issue_edit.go

@@ -70,7 +70,7 @@ func promptIssueEditProperties(requestCtx stdctx.Context, ctx *context.TeaContex
 	var labelsSelected []string
 	var err error
 
-	selectableChan := make(chan (issueSelectables), 1)
+	selectableChan := make(chan issueSelectables, 1)
 	go fetchIssueSelectables(requestCtx, ctx.Login, ctx.Owner, ctx.Repo, selectableChan)
 
 	// title