Editor + REST API for encoder templates

[connortechnology]

v2 of the encoder-templates feature (#4778). Move the hand-curated data into a new EncoderTemplates DB table, expose CRUD via a CakePHP REST API, add an Options-page editor (list / edit / copy / delete), and rename the v1 mixed Preset/Template terminology to consistently use Template.

Spec: docs/superpowers/specs/2026-05-02-encoder-templates-editor-design.md
Plan: docs/superpowers/plans/2026-05-02-encoder-templates-editor.md