chore: pin templates to v0.2.3

[Bccorb]

What

Bump the pinned seamless-templates ref from v0.2.2 to v0.2.3 in src/core/images.ts.

Why

seamless-templates v0.2.3 bumped the bundled Seamless Auth SDK versions in the starter templates (@seamless-auth/react to ^0.4.0 for TOTP support, and @seamless-auth/express to ^0.7.0, which pulls in @seamless-auth/core 0.7.0). This is the second half of the documented two-step templates-ref dance: the templates release landed first, this pins the CLI to it so seamless init scaffolds the new SDK versions.

Conformance CI is unaffected: verify-conformance.yml checks out seamless-templates at its default branch (empty templates-ref input), so it already tracks the change on main.

Verification

• npm run build passes; the compiled dist/core/images.js reflects v0.2.3.
• A changeset (patch to seamless-cli) is included.