Users can now disable a secret to stop it from being injected into
workspaces without deleting it, and re-enable it later. Disabled secrets
stay visible and editable everywhere they already appear.
An enabled secret must have at least one injection target; a secret with
no target can be stored only while disabled. Existing target-less secrets
are migrated to disabled to preserve current behavior.
Support spans the REST API, SDK, CLI, dashboard, and audit log.
Emit user secret audit log entries for create/update/delete operations.
Reads stay un-audited, matching every other resource.
Audit log entries record changes in user secret name, environment
variable name, file path, and value. The secret value column is marked
`ActionSecret` so the diff records the change without showing the
ciphertext or plaintext.
Closes a TOCTOU window on delete to ensure no phantom audit logs for a
delete of a non-existent secret. Secret update accepts a small TOCTOU
window matching the other audited resources (templates, workspaces,
chats). The two-query pattern is wrapped in a transaction so audit state
can't leak from a failed mutation.
Zach