feat: add actions management commands (#796)

## Summary

This PR adds comprehensive Actions secrets and variables management functionality to the tea CLI, enabling users to manage their repository's CI/CD configuration directly from the command line.

## Features Added

### Actions Secrets Management
- **List secrets**: `tea actions secrets list` - Display all repository action secrets
- **Create secrets**: `tea actions secrets create <name>` - Create new secrets with interactive prompts
- **Delete secrets**: `tea actions secrets delete <name>` - Remove existing secrets

### Actions Variables Management
- **List variables**: `tea actions variables list` - Display all repository action variables
- **Set variables**: `tea actions variables set <name> <value>` - Create or update variables
- **Delete variables**: `tea actions variables delete <name>` - Remove existing variables

## Implementation Details

- **Interactive prompts**: Secure input handling for sensitive secret values
- **Input validation**: Proper validation for secret/variable names and values
- **Table formatting**: Consistent output formatting with existing tea commands
- **Error handling**: Comprehensive error handling and user feedback
- **Test coverage**: Full test suite for all functionality

## Usage Examples

```bash
# Secrets management
tea actions secrets list
tea actions secrets create API_KEY    # Will prompt securely for value
tea actions secrets delete OLD_SECRET

# Variables management
tea actions variables list
tea actions variables set API_URL https://api.example.com
tea actions variables delete UNUSED_VAR
```

## Related Issue

Resolves #797

## Testing

- All new functionality includes comprehensive unit tests
- Integration with existing tea CLI patterns and conventions
- Validated against Gitea Actions API

Reviewed-on: https://gitea.com/gitea/tea/pulls/796
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Ross Golder <ross@golder.org>
Co-committed-by: Ross Golder <ross@golder.org>

cmd/actions/secrets/delete.go

@@ -0,0 +1,60 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package secrets
+
+import (
+	stdctx "context"
+	"fmt"
+
+	"code.gitea.io/tea/cmd/flags"
+	"code.gitea.io/tea/modules/context"
+
+	"github.com/urfave/cli/v3"
+)
+
+// CmdSecretsDelete represents a sub command to delete action secrets
+var CmdSecretsDelete = cli.Command{
+	Name:        "delete",
+	Aliases:     []string{"remove", "rm"},
+	Usage:       "Delete an action secret",
+	Description: "Delete a secret used by repository actions",
+	ArgsUsage:   "<secret-name>",
+	Action:      runSecretsDelete,
+	Flags: append([]cli.Flag{
+		&cli.BoolFlag{
+			Name:    "confirm",
+			Aliases: []string{"y"},
+			Usage:   "confirm deletion without prompting",
+		},
+	}, flags.AllDefaultFlags...),
+}
+
+func runSecretsDelete(ctx stdctx.Context, cmd *cli.Command) error {
+	if cmd.Args().Len() == 0 {
+		return fmt.Errorf("secret name is required")
+	}
+
+	c := context.InitCommand(cmd)
+	client := c.Login.Client()
+
+	secretName := cmd.Args().First()
+
+	if !cmd.Bool("confirm") {
+		fmt.Printf("Are you sure you want to delete secret '%s'? [y/N] ", secretName)
+		var response string
+		fmt.Scanln(&response)
+		if response != "y" && response != "Y" && response != "yes" {
+			fmt.Println("Deletion cancelled.")
+			return nil
+		}
+	}
+
+	_, err := client.DeleteRepoActionSecret(c.Owner, c.Repo, secretName)
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("Secret '%s' deleted successfully\n", secretName)
+	return nil
+}