fix 'Refresh failed: Invalid token provided' caused by token-fresher request to wrong idc

[CavemanIV]

User may experience frequently error if they use non US access point.

An IdC account has two regions and they are not always the same: the OIDC
region that issued the SSO session and refresh token, and the service
region where the CodeWhisperer profile lives. The sync layer set both to
the profile ARN's region, discarding the real OIDC region:

    const serviceRegion = extractRegionFromArn(profileArn) || ...
    const oidcRegion = serviceRegion

Since token.ts resolves auth.oidcRegion || auth.region to build the
refresh URL, every refresh for such an account went to the wrong endpoint
and failed deterministically.

Confirmed by probing both endpoints with the account's real credentials:
POST oidc.ap-southeast-1.amazonaws.com/token -> 200, expiresIn 3600
POST oidc.us-east-1.amazonaws.com/token
-> 400 invalid_request / "Invalid token provided"

The observed case is an ap-southeast-1 session paired with a us-east-1
profile ARN. The DB schema already had separate region/oidc_region
columns and token.ts already preferred oidcRegion, so only the sync layer
needed fixing.