fix: use functional setState to avoid stale closures in show-billing

[karyanayandi]

What is this PR about?

Direct reads of serverQuantity inside onClick handlers can produce stale values in closures. Use the callback form setState(prev => ...) so React always supplies the latest state value.

Checklist

Before submitting this PR, please make sure that:

• You created a dedicated branch based on the canary branch.
• You have read the suggestions in the CONTRIBUTING.md file https://github.com/Dokploy/dokploy/blob/canary/CONTRIBUTING.md#pull-request
• You have tested this PR in your local instance. If you have not tested it yet, please do so before submitting. This helps avoid wasting maintainers' time reviewing code that has not been verified by you.

Issues related (if applicable)

Screenshots (if applicable)

Greptile Summary

Fixed stale closure issue by converting setServerQuantity calls to use functional setState pattern with prev => callback, ensuring React always provides the latest state value.

• Changed decrement handler from serverQuantity - 1 to (prev) => prev <= 1 ? prev : prev - 1
• Changed increment handler from serverQuantity + 1 to (prev) => prev + 1
• This aligns with other instances in the same file that already use the functional form (lines 731, 753, 865-867, 890)

Confidence Score: 4/5

• This PR is safe to merge with minor refinement needed
• The functional setState pattern correctly addresses stale closure issues, which is a React best practice. However, there's one inconsistency where line 1083 still checks the stale serverQuantity value before calling setState - this check is now redundant since the functional setState handles the boundary condition. The button's disabled attribute already prevents invalid states, making this a low-risk issue.
• apps/dokploy/components/dashboard/settings/billing/show-billing.tsx:1083 - remove redundant stale closure check

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[greptile-apps]

this check still uses the stale serverQuantity value from the closure - if you're fixing stale closures, this line should be removed since the functional setState now handles the boundary check

Suggested change

if (serverQuantity <= 1) return;

[Copilot]

Pull request overview

This PR fixes stale closure issues in the billing component's server quantity controls by converting direct state reads to functional setState callbacks. The changes specifically target the "legacy" pricing tier's increment and decrement handlers.

Changes:

• Updated the decrement handler to use functional setState with prev parameter
• Updated the increment handler to use functional setState with prev parameter

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[Copilot]

The guard condition still reads from the stale serverQuantity closure variable instead of using the current state value. This defeats the purpose of the functional setState fix. This line should be removed since the guard is now handled inside the setState callback on line 1086.

Suggested change

if (serverQuantity <= 1) return;

[Copilot]

The decrement handler implementation is inconsistent with the existing patterns in the codebase. The "hobby" section (line 731) and "startup" section (line 865) use Math.max() for a cleaner implementation: setServerQuantity((q) => Math.max(1, q - 1)). Consider adopting the same pattern here for consistency.