RMA GeoHydro v0.3.0 — Initial stable candidate

- Set experimental=False for a proposed non-experimental initial release.
- Added interface language selector (pt_BR and en_US) and persisted preference.
- Applied glossary-based preferred terms: Embankment; Peripheral Channel; Drainage Channel; Downchute; Water Divide / Topographic Divide.
- Describes output as preliminary drainage areas, not validated catchments.
- Preserved output layer names and field schemas (including setor and alerta_geom), geometrical method and defaults for backward compatibility.
- Retained Qt6-readiness enum fixes from 0.2.5.
- Known limitation: some secondary diagnostic strings and legacy wizard prompts remain Portuguese in English mode; should be completed before public stable listing.
- Local Python compile checks only; QGIS integration, test DXFs, and upstream quality reports still required.
