refactor: remove Tor functionality

[barrydeen]

Summary

• Remove embedded kmp-tor client, all .onion relay support, Tor toggle UI (splash/auth/drawer), and Tor SOCKS plumbing from HttpClientFactory.
• Drop TorManager, TorStatus, RelayConfig.isOnionUrl/isConnectableUrl, RelayPool.swapClientAndReconnect/ensureClientCurrent, RelayLifecycleManager.onTorSwitch.
• Delete kmp-tor Gradle dependencies, ProGuard keep rules, the ic_tor_onion drawable, and 9 Tor-related string keys across 11 locales.
• Relay URL validation now accepts only wss:// with a hostname (no port, no localhost, no IP). cleartextTrafficPermitted="true" stays — still needed for local (RFC1918 / loopback) relays.

Test plan

• ./gradlew assembleDebug builds cleanly (no Kotlin/Lint errors)
• No residual references — grep -rni 'TorManager|TorStatus|kmp-tor|isOnionUrl|TorRelay|ic_tor_onion|tor_enabled|\.onion' is empty across app/, gradle/, README
• Install on device: app launches; no TorManager.initialize log noise
• Splash, Auth, side-drawer no longer show the Tor pill / onion icon button
• Relay settings: adding wss://relay.example.com works; .onion URLs are rejected by isValidUrl
• Feed loads and DMs continue to work over plain wss:// relays (no proxy applied)

Notes

• tor_enabled SharedPreferences key in wisp_settings is left as a harmless orphan on devices upgraded from a prior install — no code reads it anymore.
• Two pre-existing dead-code warnings (scope/launch in WispDrawerContent.kt) and one "condition is always true" in RelayPool.kt:1297 are unrelated to this change.