Use fuel-core 0.48.0

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PR Summary

Medium Risk
Moderate risk due to upgrading core fuel-core* crates and a large transitive dependency refresh (e.g., reqwest, thiserror, strum), which may introduce subtle behavior or build changes across services.

Overview
Upgrades tooling and builds to Rust 1.93.0 by updating the workspace rust-version, rust-toolchain.toml, CI (setup-rust action and release-plz workflow), the Makefile, docs, and the sv-dune Docker build image.

Bumps Fuel Core dependencies to 0.48 (fuel-core, fuel-core-client, fuel-core-services, fuel-core-types) and refreshes Cargo.lock with the resulting transitive updates, plus pins fuel-rust-indexer dependencies in sv-dune to a specific rev.

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