Deploy v0.14 counter contract on testnet once testnet upgrades; update counter_contract_increment address

## Context

`counter_contract_increment.rs` (and related docs/web-client tutorials) reference a hardcoded counter contract address that was deployed with v0.14 tools on devnet.

AccountId is derived from the code commitment, which uses the Poseidon2 hash function in v0.14. This means:
- v0.13-deployed contract addresses are invalid for v0.14 clients (procedure hash mismatch)
- A v0.14 contract deployed with the **same deterministic seed** on testnet will produce `mtst1XYZ` (same suffix as `mdev1XYZ`)

## Required action (when testnet upgrades to v0.14)

1. Run `deploy_counter_deterministic.rs` with the same seed against testnet RPC
2. Verify the resulting address suffix matches the devnet deployment
3. Update the hardcoded address in `rust-client/src/bin/counter_contract_increment.rs` to the combined form (following the PR #177 pattern) so it works on both networks
4. Update the same address in any docs/web-client tutorials that reference it

## Note

`counter_contract_fpi.rs` is **not affected** — it deploys in-session and requires no hardcoded address.

Find the deploy_counter_deterministic.rs script and the counter_contract_increment.rs file in rust-client/src/bin/. Run the deploy script against testnet RPC after the upgrade, verify the address suffix matches devnet, then update the hardcoded address in both the Rust client and any referenced docs or web-client tutorials. Check PR #177 for the pattern to follow for combined network addresses.

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