Feature: Implement `estimateFee` method

[Jaydbrown]

Description

Before a user clicks 'Create Stream', the UI should show them the estimated network fee.

Task

• Expose an estimateFee(operation: StreamOperation) method.
• It should run a Soroban simulation and calculate the exact fee based on the CPU/RAM usage and the current base fee.

[Aonlike]

@Aonlike has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this issue. I am a FullStack Developer. I have experience in frontend technologies such as HTML, CSS, JavaScript, React, Next.js, Tailwind CSS, and backend technologies including Node.js, Express.js, Python, Django, PHP, and Laravel.

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[adelekevictor12]

@adelekevictor12 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, i can fix this

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[GazzyLee]

@GazzyLee has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I’m interested in taking this on. I’ll add estimateFee(operation) using Soroban simulation data to calculate the expected network fee from resource usage and the current base fee, then include focused unit tests for the fee calculation and simulation flow.
ETA is in 4 hours tops, please assign

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[drips-wave]

Congratulations, @GazzyLee! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @GazzyLee: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@GazzyLee's PR #397 was approved and merged by @Jaydbrown.

🏆 @GazzyLee: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (831 total points). Track your full progress on GrantFox.

👏 Great work, @GazzyLee! Keep contributing to conduit-protocol.