CVE-2026-53603: nebula-mesh: Operator session tokens stored in plaintext in the database

Operator session tokens are stored in plaintext in the operator_sessions table (the token column is the PRIMARY KEY). The session token is a 32-byte random hex value sent directly in a cookie and valid for 24 hours.

• internal/models/operator.go:61 — OperatorSession.Token holds the plaintext token.
• internal/store/sqlite_operators.go:590 — CreateOperatorSession inserts sess.Token verbatim.
• internal/store/sqlite_operators.go:603,642,681,698 — lookups/updates/deletes use WHERE token = ? against the plaintext value.

Anyone who can read the database (backup, snapshot, file copy, or SQL-level disclosure) obtains every active session token and can hijack operator sessions directly, with no further authentication.

This is functionally identical to the plaintext enrollment-token issue fixed in GHSA-ghmh-jhmj-wcmf. API keys (OperatorAPIKey.KeyHash) and enrollment tokens (EnrollmentToken.TokenHash) already store only a SHA256 hash; session tokens were missed.