Add structured log for price snapshot write with creator ID and new price after each trade

[Chucks1093]

Summary

When the indexer updates the price snapshot after a trade, a structured log entry makes it easy to confirm prices are being written correctly without querying the database directly.

Scope

• Emit a structured debug log after each price snapshot write with fields: creator_id, new_price, previous_price, ledger_sequence, written_at
• Log only fires on successful write, not on failure
• Failure to write the snapshot should emit a separate error-level log

Acceptance Criteria

• Debug log emitted after each successful snapshot write with all fields
• Error log emitted if snapshot write fails
• No log emitted when the price is unchanged from the previous snapshot

ETA: 12 hours

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Coordinate on Telegram

[dee-john]

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Hi, I'd like to work on this issue! because I am very conversant with solving problems like this!

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[Ivenkili]

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Hey Maintainer,
I would love to work on this issue kindly assign

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[emmanueltony792-blip]

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i am capable of working on this issue perfectly

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[Muyideen-js]

@Muyideen-js has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, i can fix this

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