feat: Add new edit secret command.

[mikaeld]

Description

• Edit secrets using system's default editor (configurable via EDITOR env var)
• Content validation to prevent invalid JSON updates
• Change detection to avoid unnecessary updates
• Slight refactoring and general clean up, such as moving the preview modal screen to its own module

[Copilot]

Pull Request Overview

This PR introduces a new "edit secret" command that allows users to update secret values using their system’s default editor. Key changes include new tests in test_helpers for JSON validation and hash verification, new helper functions (validate_json_content and shasum) as well as an added add_secret_version utility in the GCP module, and significant updates to app.py to support secret editing and preview functionality.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_utils/test_helpers.py	Added tests for JSON content validation and file hash computation
secrets_manager/utils/helpers.py	Introduced utility functions for JSON validation and SHA256 checksum
secrets_manager/utils/gcp.py	Updated functions to improve secret version listing and added version creation functionality
pyproject.toml	Added new dependency "textual-dev"
app.py	Added support for editing secrets via an external editor and refactored preview functionality

[Copilot]

[nitpick] Consider quoting the file path in the os.system call to correctly handle paths with spaces. For example, wrap temp_file.name in quotes.

Suggested change

	os.system(f"{self.EDITOR} {temp_file.name}")
	os.system(f'{self.EDITOR} "{temp_file.name}"')

[mikaeld]