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/create.go

@@ -0,0 +1,96 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package secrets
+
+import (
+	stdctx "context"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"syscall"
+
+	"code.gitea.io/tea/cmd/flags"
+	"code.gitea.io/tea/modules/context"
+
+	"code.gitea.io/sdk/gitea"
+	"github.com/urfave/cli/v3"
+	"golang.org/x/term"
+)
+
+// CmdSecretsCreate represents a sub command to create action secrets
+var CmdSecretsCreate = cli.Command{
+	Name:        "create",
+	Aliases:     []string{"add", "set"},
+	Usage:       "Create an action secret",
+	Description: "Create a secret for use in repository actions and workflows",
+	ArgsUsage:   "<secret-name> [secret-value]",
+	Action:      runSecretsCreate,
+	Flags: append([]cli.Flag{
+		&cli.StringFlag{
+			Name:  "file",
+			Usage: "read secret value from file",
+		},
+		&cli.BoolFlag{
+			Name:  "stdin",
+			Usage: "read secret value from stdin",
+		},
+	}, flags.AllDefaultFlags...),
+}
+
+func runSecretsCreate(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()
+	var secretValue string
+
+	// Determine how to get the secret value
+	if cmd.String("file") != "" {
+		// Read from file
+		content, err := os.ReadFile(cmd.String("file"))
+		if err != nil {
+			return fmt.Errorf("failed to read file: %w", err)
+		}
+		secretValue = strings.TrimSpace(string(content))
+	} else if cmd.Bool("stdin") {
+		// Read from stdin
+		content, err := io.ReadAll(os.Stdin)
+		if err != nil {
+			return fmt.Errorf("failed to read from stdin: %w", err)
+		}
+		secretValue = strings.TrimSpace(string(content))
+	} else if cmd.Args().Len() >= 2 {
+		// Use provided argument
+		secretValue = cmd.Args().Get(1)
+	} else {
+		// Interactive prompt (hidden input)
+		fmt.Printf("Enter secret value for '%s': ", secretName)
+		byteValue, err := term.ReadPassword(int(syscall.Stdin))
+		if err != nil {
+			return fmt.Errorf("failed to read secret value: %w", err)
+		}
+		fmt.Println() // Add newline after hidden input
+		secretValue = string(byteValue)
+	}
+
+	if secretValue == "" {
+		return fmt.Errorf("secret value cannot be empty")
+	}
+
+	_, err := client.CreateRepoActionSecret(c.Owner, c.Repo, gitea.CreateSecretOption{
+		Name: secretName,
+		Data: secretValue,
+	})
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("Secret '%s' created successfully\n", secretName)
+	return nil
+}