* docs: add design spec for OIDC custom display name
Mirrors the existing Custom OAuth Provider name pattern so admins can
show a meaningful label instead of the hardcoded "OIDC" on the login
page and in related copy.
* feat(oidc): add configurable display name with OIDC fallback
* feat(oidc): use configured display name in provider name and status API
* feat(oidc): add display name field to default-theme OIDC settings
Claude-Session: https://claude.ai/code/session_01FDkWJqigJi9yE3HG5pjZP5
* feat(oidc): show configured display name on default-theme login button
* feat(oidc): add display name field to classic-theme OIDC settings
* feat(oidc): show configured display name on classic-theme login button
* fix(oidc): trim whitespace before applying display name fallback
* chore: remove internal design doc from PR
Design/planning docs are working artifacts for this session and
shouldn't be submitted to the upstream project.
* fix(oidc): lead with example in classic-theme display name placeholder
Reorders the combined placeholder to show the example first, then
the fallback note, matching the Custom OAuth Provider Name field's
placeholder convention (example-only) that this feature mirrors.
* fix(i18n): improve Russian grammar in OIDC display-name placeholder translation
Leads each clause with its condition/subject and adds the missing
verb, per PR review feedback.
* test(web): remove redundant OIDC harness tests
