chore: remove Namecheap secret sync solution

[xnoto]

Summary

• remove the bespoke manual Namecheap secret-sync workflow introduced by ci: add manual Namecheap secret sync workflow #33
• remove its operator and AWS prerequisite documentation

Validation

• reviewed merged PR ci: add manual Namecheap secret sync workflow #33 and current main; this branch removes only its two added files
• inspected the final deletion patches; no plaintext or decrypted secret material is present
• no secrets, existing encryption configuration, or infrastructure files were modified
• no workflow dispatches were run

[github-actions]

OpenTofu CI passed

View the workflow run.

Validation output (redacted, last 12000 characters)

Terraform validate.......................................................Passed
Terraform validate with tflint...........................................Passed
Checkov..................................................................Passed
Terraform fmt............................................................Passed
Terraform docs...........................................................Passed
Detect hardcoded secrets.................................................Passed
check for case conflicts.................................................Passed
check for merge conflicts................................................Passed
check for broken symlinks............................(no files to check)Skipped
check vcs permalinks.....................................................Passed
detect destroyed symlinks................................................Passed
detect private key.......................................................Passed
fix end of files.........................................................Passed
mixed line ending........................................................Passed
trim trailing whitespace.................................................Passed
don't commit to branch..................................................Skipped
check for added large files..............................................Passed

[github-actions]

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