docs: HTTPS setup with Caddy + OVH DNS (no Cloudflare)

## Description
Complete HTTPS setup guide using Caddy with OVH DNS plugin.
Replaces the Cloudflare-dependent default from upstream Sharkord.
OVH is French, GDPR-native, no US Cloud Act exposure.

## Deliverable
Step-by-step guide in /docs/https/ovh.md (EN + FR)