🚀 Feature: First-class self-hosted multi-region (meta + regional APIs)

### 🔖 Feature description Appwrite Cloud already models regions (`_APP_REGION`, project `region`, DB pool selection, realtime region checks, `_APP_SUPPORTS_MULTI_REGION`, etc.). Self-hosted OSS still effectively assumes a single monolith: one `regions.php` entry (`default`), one shared DB connection string for console + project pools, and no documented way to run a **meta** control plane plus **regional** API stacks that share platform data. Please make self-hosted multi-region a supported, documented configuration—without requiring private configs/image hotfixes. ### 🎤 Pitch Self-hosters who need data residency / geo latency / want Cloud-like topology: 1. **Meta** – platform/console MariaDB + apex API (orgs, projects, accounts) 2. **Regional APIs** – local project MariaDB + full workers; `_APP_DB_*` / console pool pointed at meta MariaDB 3. Console talks to regional hosts based on project `region` Today this is only possible with fragile overrides. Official env + config support would unlock HA/geo deployments and match Cloud semantics where OSS already has hooks. ### 👍 Solution / proposed scope Discuss and (if accepted) implement first-class support for: 1. **Configurable region catalog** – via environment (e.g. JSON), without requiring users to edit `app/config/regions.php` inside the image. 2. **Split / multi DB pools on meta** – document and support `_APP_CONNECTIONS_DATABASE` (or successor) so meta can register **platform** + **per-region project** pools, not a single DSN for everything. 3. **Cross-region project create** – document `_APP_DATABASE_KEYS` (Utopia pool names like `database_db_fra_main`) so Create Project can `$pools->get()` the correct regional DB from meta. 4. **Regional process identity** – `_APP_REGION=<id>` on each regional stack; platform DB host separate from local project MariaDB. 5. **Console variables** – expose multi-region capability + safe domain targets (`_APP_DOMAIN_TARGET_CNAME`, etc.) so `/v1/console/variables` works for self-ho…