docs: scrub internal host references from public docs

Removed mentions of dedicated servers + Sulkta-runs-its-own-Koios claims from
README + module doc-comments + Cargo.toml descriptions. aldabra works
against any Koios endpoint — public api.koios.rest, preprod/preview,
or operator-self-hosted — so the docs now reflect that capability
neutrally instead of advertising our internal infra.

crates/aldabra-chain/src/lib.rs

@@ -12,8 +12,10 @@
 //! ## Backends
 //!
 //! - [`koios::KoiosClient`] — Koios REST client (POST `/address_utxos`,
-//!   `/address_info`). Sulkta runs its own Koios on dedicated servers; the
-//!   public `https://api.koios.rest/api/v1` works as a fallback.
+//!   `/address_info`). Points at any Koios endpoint —
+//!   `https://api.koios.rest/api/v1` for the public mainnet instance,
+//!   the preprod/preview equivalents for testnets, or a self-hosted
+//!   Koios at any URL.
 //! - Ogmios (TODO) — websocket client.
 
 use serde::{Deserialize, Serialize};