Implement price-feed feature

[zahorodnyi]

Usage: cargo run -p cli-client price-feed

Fix: #40

[zahorodnyi]

@greptile review the PR according to the CONTRIBUTION.md

[greptile-apps]

Greptile Summary

Adds a new price-feed command to fetch and display the current BTC/USD price from CoinGecko API. The implementation uses a clean separation of concerns with a PriceFetcher trait, error handling via custom PriceFetcherError enum, and async/blocking task management. The feature integrates seamlessly into the existing CLI command structure.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation is straightforward, uses proper error handling, follows existing codebase patterns, and introduces no breaking changes. The single commit is logical and self-contained per the repository's custom instruction.
• No files require special attention

Important Files Changed

Filename	Overview
crates/cli-client/src/price_fetcher.rs	Adds CoingeckoPriceFetcher that fetches BTC/USD price from CoinGecko API with error handling and timeout
crates/cli-client/src/cli/price.rs	Implements async run_price_feed() function that fetches and displays BTC/USD price using spawn_blocking

Sequence Diagram

sequenceDiagram
    participant User
    participant CLI
    participant PriceModule as price::run_price_feed()
    participant Fetcher as CoingeckoPriceFetcher
    participant API as CoinGecko API

    User->>CLI: cargo run -p cli-client price-feed
    CLI->>PriceModule: Command::PriceFeed
    PriceModule->>Fetcher: new()
    PriceModule->>PriceModule: spawn_blocking()
    activate PriceModule
    PriceModule->>Fetcher: fetch_price()
    Fetcher->>API: GET /api/v3/simple/price?ids=bitcoin&vs_currencies=usd
    API-->>Fetcher: {"bitcoin": {"usd": 95234.56}}
    Fetcher-->>PriceModule: Ok(PriceMap)
    deactivate PriceModule
    PriceModule->>PriceModule: Extract bitcoin/usd from response
    PriceModule->>User: println!("1 BTC = $95234.56")

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[greptile-apps]

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[greptile-apps]

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