fix(perps): handle liquidation price request failures

[SeniorZhai]

Summary

• retry liquidation price estimates only when the API returns error code 500
• stop after non-500 failures and display - on open/add position screens
• skip liquidation price requests when the entered margin is below minAmount
• share the retry policy between both screens and cover it with unit tests

Root cause

Both position screens treated every failed estimate as a temporary failure and retried indefinitely. The ViewModel returned only a nullable price, so callers could not distinguish server errors from non-retryable failures.

User impact

Open and add-position screens no longer repeatedly request liquidation prices for non-500 errors, and invalid below-minimum amounts do not trigger the estimate API.

Validation

• ./gradlew :app:testGooglePlayDebugUnitTest --tests one.mixin.android.ui.home.web3.trade.perps.LiquidationPriceRequestTest

[Copilot]

Pull request overview

Updates liquidation-price estimation to avoid unnecessary retries and invalid requests.

Changes:

• Retry only error code 500; stop on other failures.
• Skip estimates below the market minimum.
• Share and unit-test retry/request policy.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
LiquidationPriceRequestTest.kt	Tests retry and minimum-amount behavior.
PerpsAddBottomSheetDialogFragment.kt	Applies shared policy to add-position estimates.
PerpetualViewModel.kt	Returns structured estimation results.
OpenPositionPage.kt	Applies minimum validation and retry handling.
LiquidationPriceRequest.kt	Defines shared result and retry logic.

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