Allow administrators to reconfigure Linear OAuth

[daniel-lxs]

Summary

• keep Linear OAuth credential management available to deployment administrators after initial configuration
• use a compact settings action so the Linear card retains the shared integration-card layout
• preserve the generic Reconnect action for connected Linear workspaces
• allow stored credentials to be replaced without exposing their current values
• add a confirmed removal flow that disables Linear and clears only credentials stored by Roomote
• keep runtime environment credentials read-only and clearly identify their source
• document the reconfiguration behavior

Validation

• focused Linear command and integrations UI tests (65 tests)
• @roomote/web typecheck
• ESLint on changed web files
• formatting and diff checks

[roomote-roomote]

No new code issues found. See task

_{Reviewed e6b8dae}