Remove fastly from core crate

[aram356]

Description

Remove all fastly imports from trusted-server-core. Delete compat.rs compatibility adapter. Remove tokio dependency from core crate.

tokio removal

crates/trusted-server-core/Cargo.toml has tokio = { workspace = true }. Core targeting wasm32-wasip1 and wasm32-unknown-unknown must not depend on tokio. Audit test code using #[tokio::test] — replace with a wasm-compatible test harness or move those tests to adapter crates where tokio is available.

Done when

• Core has zero fastly imports
• Core has zero tokio imports; tokio removed from core Cargo.toml
• compat.rs deleted
• Per-PR gates pass

Blocked by

PR 14

References

• docs/internal/EDGEZERO_MIGRATION.md — Phase 3, PR 15
• Part of EdgeZero migration #480