Implement centralized shutdown handling for graceful application termination

[doganarif]

What's fixed

• Replace multiple signal handlers with single centralized handler using sync.Once
• Add shutdown function registry with thread-safe access
• Improve error handling and context propagation during shutdown
• Eliminate race conditions from competing signal handlers

fixes #26

Summary by Sourcery

Implement a single centralized shutdown mechanism using sync.Once and a thread-safe function registry, migrating existing cleanup routines into this mechanism for consistent graceful application termination.

New Features:

• Add centralized signal handler and shutdown function registry for graceful application termination.

Bug Fixes:

• Eliminate race conditions by replacing multiple competing signal handlers with a single handler.

Enhancements:

• Register storage and telemetry cleanup functions in a thread-safe registry.
• Improve context propagation and error logging during shutdown execution.

[sourcery-ai]

Reviewer's Guide

Refactors graceful shutdown by centralizing all signal handling into a single, thread-safe registry using sync.Once and a shutdown function list; replaces inline per-component handlers in Wrap() with addShutdownFunc registrations; and improves error reporting and context usage during shutdown.

File-Level Changes

Change	Details	Files
Centralize signal handling and registry	Introduce signalOnce to ensure one-time setup Add shutdownFuncs slice with shutdownMutex for thread safety Implement addShutdownFunc and setupSignalHandler functions	wrap.go
Replace ad-hoc per-component handlers with registry registrations	Remove inline goroutines for requestStore.Close() signal handling Remove individual telemetry shutdown listener Use addShutdownFunc to register store and telemetry cleanup Call setupSignalHandler once at end of Wrap()	wrap.go
Improve error handling and context propagation in shutdown	Change cleanup callbacks to return errors and log failures Use context.Background() uniformly for shutdown functions	wrap.go

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[sourcery-ai]

Hey @doganarif - I've reviewed your changes - here's some feedback:

• Consider invoking each shutdown function with a context that has a timeout (e.g. context.WithTimeout) instead of Background so that a stuck cleanup routine can’t block the exit.
• Since Wrap may be called multiple times, you could end up registering duplicate shutdown handlers; consider deduplicating or moving the registration out of the per-handler initialization.
• If resource teardown order matters, you might want to execute shutdownFuncs in reverse registration order (LIFO) to ensure dependencies are cleaned up properly.

Here's what I looked at during the review

• 🟡 General issues: 1 issue found
• 🟢 Testing: all looks good
• 🟢 Documentation: all looks good

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