Fix Dashlane Cloudflare captcha by implementing official CLI protocol

[detunized]

Fixes #180

The old Dashlane protocol was triggering Cloudflare captcha protection, which returned HTML instead of JSON and caused parsing errors.

This PR implements a new protocol that mimics the official Dashlane CLI to avoid triggering captcha protection.

Changes

• Reworked Dashlane client to use official CLI protocol
• Added proper MFA retry logic with better error messages
• Improved test coverage for authentication flows

[gitguardian]

⚠️ GitGuardian has uncovered 5 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
21216985	Triggered	Generic High Entropy Secret	884166d	test/Dashlane/Fixtures/perform-totp-verification.json	View secret
21216986	Triggered	Generic High Entropy Secret	884166d	test/Dashlane/Fixtures/complete-device-registration-with-server-key.json	View secret
21216987	Triggered	Generic High Entropy Secret	884166d	test/Dashlane/Fixtures/complete-device-registration-with-auth-ticket.json	View secret
21216988	Triggered	Generic High Entropy Secret	884166d	test/Dashlane/Fixtures/complete-device-registration-with-server-key.json	View secret
21216989	Triggered	Generic High Entropy Secret	884166d	test/Dashlane/VaultTest.cs	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.}