Add a conditions lock option to Schema Templates

### Problem description
Template config has no lock for conditions.

### Requirements
- Add `conditionsLocked` toggle (config + UI), allowing all condition edits; adding a new field in a branch still needs `customFieldsLocked=false`.
- Per-field lock toggles for fields inside conditions, like regular fields.
- Fix template custom conditions/fields updating.

### Definition of done
`conditionsLocked` allows edit the Conditions tab as specified, and template updates preserve or flag policy-authored condition work instead of silently dropping it.

### Acceptance criteria
- [ ] `conditionsLocked` toggles per schema and persists.
- [ ] Locked = no condition add/edit/remove; unlocked + `customFieldsLocked` = edit only, no new fields.
- [ ] Per-field lock toggles work inside conditions.
- [ ] Resolving condition changes conflicts when updating template.
- [ ] Tests cover the above in the existing `schema-template-*` unit test files.