Add synchronous IndexedMap support for remote stores

[forhappy]

Summary

• add a shared BlockingRemoteProllyStore that exposes the synchronous Store, manifest, scan, strict transaction, and IndexedStore contracts over native async remote backends
• add first-class Sync*Store aliases for PostgreSQL, MySQL, Redis, Turso, DynamoDB, Cosmos DB, and Spanner
• safely bridge calls made inside existing Tokio runtimes and own provider runtime lifecycle, including clean final drop from async contexts
• extend every provider conformance suite with the real synchronous engine.indexed_map(...) workflow and document production usage

Correctness

IndexedMap continues to pre-publish immutable content-addressed nodes, then validates and advances its sole canonical collection root through the provider native strict transaction. A conflict publishes no visible state. This keeps the visibility transaction small for DynamoDB and Cosmos DB service limits while preserving immediate readability after an applied root.

Verification

• cargo test --features tokio
• cargo clippy --features tokio --all-targets -- -D warnings
• cargo +1.89.0 check --features tokio --all-targets
• RUSTDOCFLAGS=-D warnings cargo doc --no-deps --features tokio
• default-feature cargo check --all-targets
• all seven adapter crates: cargo check --all-targets, strict clippy, and doctests
• Turso local synchronous IndexedMap integration test
• PostgreSQL, MySQL, Redis, DynamoDB, Cosmos DB, and Spanner live IndexedMap conformance tests remain credential-gated
• ./scripts/check-secondary-index-cutover.sh