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>

internal/version/version.go

@@ -0,0 +1,33 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package version
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+// Version holds the current tea version.
+// This is set at build time via ldflags.
+// If the Version is moved to another package or name changed,
+// build flags in .goreleaser.yaml or Makefile need to be updated accordingly.
+var Version = "development"
+
+// Tags holds the build tags used
+var Tags = ""
+
+// Format returns a human-readable version string including
+// Go version and build tags when available.
+func Format() string {
+	s := fmt.Sprintf("Version: %s\tgolang: %s",
+		Version,
+		strings.ReplaceAll(runtime.Version(), "go", ""))
+
+	if len(Tags) != 0 {
+		s += fmt.Sprintf("\tbuilt with: %s", strings.ReplaceAll(Tags, " ", ", "))
+	}
+
+	return s
+}