fix(mobile): Remote video playback and asset download on Android with mTLS

[rovo89]

Description

This is a first stab at supporting remote video playback and asset download for servers which require a client certificate (mTLS). Some discussions about this topic can be found in #15230.

The underlying problem is that these parts of the app don't use Dart's HTTPS client, but the native one, which obviously doesn't care about the HttpOverride. This (Android-only) implementation does a similar thing though by setting the default SSL context for the native sockets.

It shouldn't be a big deal to allow self-signed certificates by providing a TrustManager, but I first want to be sure that this approach is acceptable.

The only feasible alternative seems to be switchiting to cronet, but I think my way is much less intrusive.

How Has This Been Tested?

I've configured my nginx reverse proxy to require mTLS and it's working fine with that. Further tests to be done for "normal" setups and iOS (I only have Android though).

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if applicable
• I have no unrelated changes in the PR.
• I have confirmed that any new dependencies are strictly necessary.
• I have written tests for new code (if applicable)
• I have followed naming conventions/patterns in the surrounding code
• All code in src/services uses repositories implementations for database calls, filesystem operations, etc.
• All code in src/repositories/ is pretty basic/simple and does not have any immich specific logic (that belongs in src/services)

[github-actions]

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