feat: adds support for price SSE stream

[stalniy]

Why

Ref AKA-175

What

1. adds new PRICE_FETCHING_METHOD variable
2. adds support for parsing price updates from Pyth SSE

[Copilot]

Pull request overview

Adds a new Hermes price streaming mode using Server-Sent Events (SSE), selectable via a new PRICE_FETCHING_METHOD config value, and refactors shared Hermes response parsing into a utility.

Changes:

• Introduces priceSSEStream() to consume /v2/updates/price/stream and yield PriceUpdates with retry/reconnect handling.
• Adds PRICE_FETCHING_METHOD (polling | sse) to CLI config parsing and documents it in the README.
• Refactors Hermes response parsing into parsePriceUpdate() and reuses it in both polling and SSE streams.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/price-stream/utils.ts	Adds shared Hermes HermesResponse → PriceUpdate parsing helper.
src/price-stream/price-sse-stream/price-sse-stream.ts	Implements SSE-based price stream with retry and Last-Event-ID support.
src/price-stream/price-sse-stream/price-sse-stream.test.ts	Adds comprehensive unit tests for SSE stream behavior.
src/price-stream/polling-price-stream/polling-price-stream.ts	Reuses shared parsing and improves JSON parse error handling; removes console noise.
src/price-stream/polling-price-stream/polling-price-stream.test.ts	Updates imports and removes log-detail test tied to removed logging.
src/hermes-client.ts	Adds logging for received price updates (applies to both polling and SSE).
src/cli-commands/command-config.ts	Adds PRICE_FETCHING_METHOD and switches producer factory based on it.
package.json / package-lock.json	Adds fetch-event-stream dependency for SSE parsing.
README.md	Documents PRICE_FETCHING_METHOD.

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