Drop iOS Application Integrated with Firebase

[oluiscabral]

Branched off from the last commit of #4 (ef81c65)

Integrates Firebase Analytics and Crashlytics.

Cover the whole Send Files and Receive Files use cases with Firebase Crashlytics logs

[mdrlzy]

@oluiscabral

I tested iOS app. Logs might be useful.

Receiving files works as expected, but sending files causes crash:

SenderFileDataImpl: Initializing file
SenderFileDataImpl: Created URL
SenderFileDataImpl: File size: 1581467 bytes
SenderFileDataImpl: Stream status: 2
SenderFileDataImpl: Successfully initialized
✅ Successfully decoded QR code (25254 bytes)
⚠️ ArkDropSenderFileDataAdapter.readChunk() error: kotlin.ArrayIndexOutOfBoundsException

thread '<unnamed>' (17417648) panicked at drop-core/exchanges/sender/src/send_files.rs:119:13:
there is no reactor running, must be called from the context of a Tokio 1.x runtime
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
ArkDrop/ArkDrop.swift:1779: Fatal error: 'try!' expression unexpectedly raised an error: ArkDrop.(unknown context at $10a1d4b98).UniffiInternalError.rustPanic("there is no reactor running, must be called from the context of a Tokio 1.x runtime")

It’s strange that I don’t get the same issue on Android. I asked ChatGPT:

The problem is that on Android the Tokio runtime context probably exists either accidentally or because of the current architecture. On iOS, because of the Obj-C -> Kotlin -> Swift callback chain, Rust may be called from a thread without a Tokio reactor.
A more reliable fix would be to avoid using global tokio::spawn / Handle::current() calls in library code, and instead always spawn tasks through the stored Runtime or Handle.
Also, self.runtime.enter() may not be enough here, because it only enters the runtime for the current thread while the guard is alive. If the flow continues later from another thread or callback, the same issue may still happen.

It looks like the issue may be caused by switching threads due to the language bridge or Kotlin coroutines.