Initial commit: Deepwave Phase 1 - auth scaffolding

Spotify-like Navidrome client scaffold with Hilt DI, a Subsonic API
client (token auth, base-URL rewriting), encrypted single-server
credential storage (DataStore + Tink/Keystore), and a login/session
flow gating Compose Navigation between Login and a placeholder Home
screen.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/src/main/res/xml/backup_rules.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+   Sample backup rules file; uncomment and customize as necessary.
+   See https://developer.android.com/guide/topics/data/autobackup
+   for details.
+   Note: This file is ignored for devices older than API 31
+   See https://developer.android.com/about/versions/12/backup-restore
+-->
+<full-backup-content>
+    <!--
+   <include domain="sharedpref" path="."/>
+   <exclude domain="sharedpref" path="device.xml"/>
+-->
+</full-backup-content>