test(calling): stabilize registration Playwright tests

[vivekv1504]

COMPLETES #< NO JIRA ISSUE >

This pull request addresses

Flaky registration Playwright tests caused by inconsistent HTTP/WebSocket configuration, outdated hard-coded Mobius URLs, and long production retry intervals during failover testing.

by making the following changes

• Explicitly configures HTTP or WebSocket mode during SDK initialization.
• Discovers current primary and backup Mobius URLs dynamically.
• Updates failover tests to intercept only the discovered primary server.
• Fixes REG-016 to validate failover against the discovered backup server.
• Makes REG-017 retry timing deterministic while still verifying all five 429 attempts.
• Reduces unnecessary waiting and restores production retry behavior after the test.
• Keeps the unsupported INT guest-registration scenario intentionally skipped.

Change Type

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tooling change
• Internal code refactor

The following scenarios were tested

< ENUMERATE TESTS PERFORMED, WHETHER MANUAL OR AUTOMATED >

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• GAI was not used (or, no additional notation is required)
• Code was generated entirely by GAI
• GAI was used to create a draft that was subsequently customized or modified
• Coder created a draft manually that was non-substantively modified by GAI (e.g., refactoring was performed by GAI on manually written code)
• Tool used for AI assistance (GitHub Copilot / Other - specify)
  • Github Copilot
  • Other - Please Specify
• This PR is related to
  • Feature
  • Defect fix
  • Tech Debt
  • Automation

I certified that

• I have read and followed contributing guidelines
• I discussed changes with code owners prior to submitting this pull request
• I have not skipped any automated checks
• All existing and new tests passed
• I have updated the documentation accordingly

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