Unify frontend update passwords into CLIENT_MASTER_PASSWORD and update AWS env

[justin-phxm]

We currently have multiple frontend passwords configured as separate environment variables:

• DRIVER_NAME_UPDATE_PASSWORD=changeme
• FINISH_LINE_UPDATE_PASSWORD=changeme

Proposal

Unify these into a single environment variable used by the frontend and backend for client update operations, e.g.:

CLIENT_MASTER_PASSWORD=changeme

Benefits

• Simplifies password management (only one password to remember/rotate)
• Reduces configuration mistakes from inconsistent passwords across variables
• Easier rotation: update a single environment variable in AWS

Scope / Tasks

• Update frontend code to read CLIENT_MASTER_PASSWORD everywhere DRIVER_NAME_UPDATE_PASSWORD and FINISH_LINE_UPDATE_PASSWORD are used
• Update backend (if applicable) to accept/validate CLIENT_MASTER_PASSWORD
• Update CI/deployment and AWS environment configuration to set CLIENT_MASTER_PASSWORD and remove the old variables
• Add a short migration note in repository docs / README describing the change and the steps to rotate the password
• Test: verify all password-protected FE actions still work against the new env var, and old env vars are no longer required

Migration notes

• During rollout, set both old variables and the new CLIENT_MASTER_PASSWORD to the same value to avoid downtime, then remove the old variables once verified
• Coordinate deployment with whoever manages the AWS environment variables

Acceptance criteria

• All FE password-protected actions use CLIENT_MASTER_PASSWORD and work as expected
• DRIVER_NAME_UPDATE_PASSWORD and FINISH_LINE_UPDATE_PASSWORD are removed from production AWS environment
• README or docs updated with instructions on how to rotate CLIENT_MASTER_PASSWORD

Risks

• If the backend expects different passwords for different actions, this change will require backend validation updates; confirm compatibility first