feat(ssh-keys): add ssh-keys command to manage SSH public keys (#940)

## Summary

- Adds `tea ssh-keys` command group (aliases: `ssh-key`, `keys`) under the SETUP category
- Mirrors the interface of `gh ssh-key add/list/delete`
- Three subcommands: `add <keyfile>`, `list`, `delete <id>`

## Commands

\`\`\`sh
tea ssh-keys add ~/.ssh/id_ed25519.pub                     # title defaults to filename stem
tea ssh-keys add ~/.ssh/id_rsa.pub --title "work laptop"
tea ssh-keys add ~/.ssh/deploy.pub --read-only             # authentication-only key
tea ssh-keys list
tea ssh-keys list --output json
tea ssh-keys delete 42                                     # prompts for confirmation
tea ssh-keys delete 42 --force                             # skip prompt
\`\`\`

## Test plan

- [x] `make lint` — 0 issues
- [x] `make fmt-check` — passes
- [x] `go test ./cmd/sshkeys/... -run TestKeyTitle` — unit tests pass (no server needed)
- [ ] Integration tests with live Gitea instance:
  \`\`\`sh
  GITEA_TEA_TEST_URL=https://your-gitea \
  GITEA_TEA_TEST_TOKEN=<token> \
  go test ./cmd/sshkeys/... -v -run TestSSHKey
  \`\`\`
  Exercises full add → SDK-verify → delete → 404-verify lifecycle.

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Brandon Fryslie <530235+brandon-fryslie@users.noreply.github.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/940
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Brandon Fryslie <186614+brandroid@noreply.gitea.com>
Co-committed-by: Brandon Fryslie <186614+brandroid@noreply.gitea.com>

cmd/sshkeys/add.go

@@ -0,0 +1,74 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package sshkeys
+
+import (
+	stdctx "context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"code.gitea.io/sdk/gitea"
+	"code.gitea.io/tea/cmd/flags"
+	"code.gitea.io/tea/modules/context"
+
+	"github.com/urfave/cli/v3"
+)
+
+// CmdSSHKeyAdd represents a sub command of ssh-keys to add an SSH public key
+var CmdSSHKeyAdd = cli.Command{
+	Name:        "add",
+	Usage:       "Add an SSH public key",
+	Description: "Add an SSH public key to the current user's profile",
+	ArgsUsage:   "<key-file>",
+	Action:      RunSSHKeyAdd,
+	Flags: append([]cli.Flag{
+		&cli.StringFlag{
+			Name:    "title",
+			Aliases: []string{"t"},
+			Usage:   "Title for the key (defaults to the filename without extension)",
+		},
+	}, flags.LoginOutputFlags...),
+}
+
+// RunSSHKeyAdd reads a public key file and registers it with the Gitea instance
+func RunSSHKeyAdd(_ stdctx.Context, cmd *cli.Command) error {
+	ctx, err := context.InitCommand(cmd)
+	if err != nil {
+		return err
+	}
+
+	if ctx.Args().Len() < 1 {
+		return fmt.Errorf("key file path is required")
+	}
+
+	keyFile := ctx.Args().First()
+	keyBytes, err := os.ReadFile(keyFile)
+	if err != nil {
+		return fmt.Errorf("could not read key file '%s': %w", keyFile, err)
+	}
+
+	keyContent := strings.TrimSpace(string(keyBytes))
+	if keyContent == "" {
+		return fmt.Errorf("key file '%s' is empty", keyFile)
+	}
+
+	title := ctx.String("title")
+	if title == "" {
+		base := filepath.Base(keyFile)
+		title = strings.TrimSuffix(base, filepath.Ext(base))
+	}
+
+	key, _, err := ctx.Login.Client().CreatePublicKey(gitea.CreateKeyOption{
+		Title: title,
+		Key:   keyContent,
+	})
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("Key '%s' (id: %d) added successfully.\n", key.Title, key.ID)
+	return nil
+}