Add offline-mode protocol adapters, session manager, UI connect flow and launcher branding

[WieszczY85]

Motivation

• Implement a real (headless) networking prototype so the app can perform offline-mode Minecraft logins and basic session management instead of only using demo data.
• Provide a clear domain-facing session contract and map protocol failures to safe UI-facing errors.
• Expose a quick connect UI and integrate a branded launcher and logo assets for a presentable prototype.

Description

• Add a packet-independent protocol boundary and typed session model by introducing MinecraftConnection (now returning ConnectedSession) and MinecraftConnectionException, plus SessionManager/SessionManagerFactory and domain models in domain/session.
• Implement a concrete session manager DefaultSessionManager that serializes lifecycle operations, publishes StateFlow snapshots and emits SharedFlow events, and maps connection exceptions to SessionError.
• Provide two offline-mode protocol adapters: protocol.modern.ModernOfflineMinecraftConnection (Minecraft Java 26.1 / protocol 775) and protocol.legacy.LegacyOfflineMinecraftConnection (protocol 47) with a shared ProtocolCodec for framing, varint/strings, and compression handling.
• Wire the session system into UI: CraftConnectApp now accepts a SessionManagerFactory, ServersScreen shows an offline quick-connect dialog, and ChatScreen forwards send actions to the active session manager.
• Add launcher/branding assets and theme entries (craftconnect_logo, adaptive ic_launcher/ic_launcher_round, colors and values-v31/themes.xml) and update BrandHeader to show the logo.
• Update README.md and docs/ARCHITECTURE.md to document the protocol scope and session abstraction, and update Gradle libs and app/build.gradle.kts to add coroutine and test dependencies.

Testing

• Added unit and integration-style tests and executed them: ProtocolCodecTest, LegacyOfflineMinecraftConnectionTest, ModernOfflineMinecraftConnectionTest, and DefaultSessionManagerTest.
• All added tests ran as part of the Gradle test suite and passed.
• Verified Gradle build with ./gradlew :app:assembleDebug after dependency updates and resource additions.

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Codex Task