feat: add bitcoin integration template

[marc0olo]

Summary

Add a Bitcoin integration template demonstrating how to read Bitcoin balance from a canister using the Bitcoin canister API.

• Rust backend uses ic_cdk::bitcoin_canister which handles cycle costs and canister ID selection automatically
• Motoko backend calls the Bitcoin canister directly with (with cycles = amount) syntax (moc 1.1.0, mo:core)
• Two endpoints: get_balance (returns satoshi balance) and get_config (returns configured network + Bitcoin canister ID)
• Three environments via BITCOIN_NETWORK env var: local (regtest), staging (testnet), production (mainnet)
• Network type selection (Default vs Docker) with correct bitcoind-addr handling (127.0.0.1 for native, host.docker.internal via args for Docker)
• README with Bitcoin canister IDs table, getting started guide, cycle costs reference, and environment overview
• Rust recipe pinned to @dfinity/rust@v3.0.0, Motoko recipe points to icp-cli-recipes main branch (for now)

Dependenies

This PR relies on following PRs and shouldn't be merged until those are released:

• fix: implicit bitcoin and dogecoin setup when passing node addresses icp-cli-network-launcher#22 (merged, but not released yet)
• feat: add bitcoind-addr and dogecoind-addr to managed launcher config icp-cli#347

[marc0olo]

using this to avoid the requirement for optional args. we should switch once a new release of Motoko recipe is out

[marc0olo]

wondering if we should name it bitcoin-integration instead. I am generally wondering if we should introduce a convention for all the examples and have a clear rule regarding the ordering.