feat(site-manager): add show/hide password toggle button

[Orinks]

Adds a Show/Hide button next to the password field in the Site Manager dialog.

• Clicking Show replaces the masked TE_PASSWORD field with a plain text field, revealing the password
• Clicking Hide switches back to masked
• Current value is preserved across toggles
• Button label and accessible name update (Show password / Hide password) so screen readers announce the state correctly
• Focus moves to the password field after toggling

[gitguardian]

⚠️ GitGuardian has uncovered 2 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
27704466	Triggered	Generic Password	dbf9201	src/portkeydrop/dialogs/site_manager.py	View secret
27704467	Triggered	Generic Password	dbf9201	src/portkeydrop/dialogs/site_manager.py	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secrets safely. Learn here the best practices.
3. Revoke and rotate these secrets.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}