Add CODE_OF_CONDUCT.md with a stance on religious disagreement

[eaitbrahim]

A project inviting international contributors around a religious topic needs a stated behavioural baseline before it needs one.

Acceptance

• CODE_OF_CONDUCT.md — Contributor Covenant is the sane default; do not write one from scratch
• A named enforcement contact that actually reaches someone
• One project-specific addition worth making explicit: disagreement about a religious ruling is expected and legitimate; disparaging another madhhab, school, or a contributor's practice is not. The technical route for disagreement is a local attestation or exception, not an argument in a thread