Proxy: fix proxy settings not reactively applied in UnauthorizedAccount

[mvsrcdst]

Problem

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If user changes/switch proxy settings mid-login before authorization completes, the change isn't picked up and the app keeps using the proxy config it had at login start. Only workaround: restart the app.

Root cause: Account (post-login) already has a reactive subscription to SharedDataKeys.proxySettings that pushes proxy changes into the live MTProto network environment. UnauthorizedAccount (pre-login) had no equivalent, proxy settings were read once at init and effectively frozen for the rest of the login flow.

Fix

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Add the same reactive subscription to UnauthorizedAccount that Account already has:

• subscribe to SharedDataKeys.proxySettings, distinctUntilChanged
• on change, compare current vs updated MTSocksProxySettings
• if different, drop connection status and push the updated settings into network.context's API env

Tracked with MetaDisposable, disposed in deinit.

Impact

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Switching/changing SOCKS5 proxy mid-login now takes effect immediately, no app restart needed.

Note

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Part of tracking issue: #182

Testing

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• Tested on iOS Simulator 18.6/26.5
• Start login flow, open proxy connection settings, set proxy, confirm connection recovers without restart app