Replace webprotege-local.edu with a reserved local-dev TLD (webprotege.test)

[matthewhorridge]

Problem

The default local hostname across the stack is `webprotege-local.edu`. `.edu` is a real, accredited-institution TLD registered through EDUCAUSE, not a safe-for-local namespace. Using it here is:

• Non-standard — RFC 2606 reserves `.test`, `.example`, `.invalid`, `.localhost` for exactly this use case. `.edu` isn't in that list.
• A latent DNS-hijack surface — if anyone in the network chain ever routes `.edu` queries externally, or if `webprotege-local.edu` is ever registered as a real subdomain, requests could leak.
• Slightly misleading — it reads as if it's a real Stanford/EDUCAUSE subdomain.

There's also an internal inconsistency surfaced during the 2.x migration: the user-facing `SERVER_HOST` in some developers' `.env` was `webprotege.local`, while the defaults shipped in the realm JSON, the gateway's `application.yaml`, and (previously) docker-compose.yml were `webprotege-local.edu`. The mismatch caused a real bug (the gateway crashed because Keycloak's discovery doc returned the .edu issuer while the gateway was configured for `webprotege.local`).

Suggested fix

Standardize on `webprotege.test` (RFC 2606 reserved, collision-safe, reads clearly as local-dev).

Touch points:

• `webprotege-deploy/.env.example` — default `SERVER_HOST`.
• `webprotege-deploy/README.md` — hosts file instructions.
• `webprotege-keycloak/webprotege.json` — realm `frontendUrl` attribute, webprotege client `baseUrl`/`redirectUris`/`webOrigins`, `smtpServer.from`.
• `webprotege-gwt-api-gateway/src/main/resources/application.yaml` — four `webprotege-local.edu` references (tracked separately in Remove hardcoded webprotege-local.edu from application.yaml webprotege-gwt-api-gateway#45).

Existing developers would need to update their `/etc/hosts` (swap the line) and either update their `.env` or rely on the new default. No runtime migration beyond that — the new realm/client URIs get applied by the existing entrypoint patch script when `SERVER_HOST` changes.

Alternative

`webprotege.localhost` — on many systems (macOS, Linux with systemd-resolved) `*.localhost` auto-resolves to 127.0.0.1 so no `/etc/hosts` entry is needed. But support isn't universal, so `.test` is the safer baseline.