fix(ios): clear authorization callbacks before invoking them

[OskarEichler]

Fixes: one-shot authorization callbacks and safe button callbacks

• Clear the stored authorization completion before calling it, while retaining a local copy for invocation. Reentrant or late callbacks cannot invoke an already-consumed block; completion is not accessed after the owning delegate can be released.
• Do not invoke the button event block when React has not attached it or has removed it.

Compatibility

No public API changes. Authorization settles once, and a button without an attached callback does nothing instead of dereferencing a null block.

Reproduction

Compiled the actual Objective-C callback bodies against Foundation. A reentrant error callback runs twice before the fix and once after; the completion is cleared. Late callbacks, missing button callbacks and an attached button callback are also exercised after the fix.

Verification

• Upstream ESLint and existing TypeScript usage checks pass.
• Focused inline reproductions compare unchanged 5f7a8d7 with the fix; no test/spec files were changed.
• React Doctor reports 100/100 on the changed JavaScript scope.
• Consumer verification now passes on React Native 0.87.1: both Android Debug flavors, both iOS Simulator Debug schemes (unsigned), all four production-mode Metro bundles, immutable Yarn install and app lint. All seven changed installed source files match the verified fork.
• No real Apple sign-in, account changes, physical-device authentication, macOS/visionOS runtime checks or signed release archives were performed.

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