Security hardening + code-review fixes

Outcome of a full multi-agent code review. Touches TLS, credential storage,
API versioning, networking correctness, concurrency/lifecycle, and the release
build. See CHANGELOG.md for the full list and the items to port to the iOS app.

Security
- Remove untrusted-TLS support: delete ServerTrustPolicy.AllowSelfSignedForHost
  and its trust-all X509TrustManager; drop the self-signed Settings toggle.
- Enforce HTTPS in normalizedBaseUrl (reject http + embedded credentials);
  add network_security_config (no cleartext, system CAs only) + allowBackup=false.
- Never persist passwords at rest: remember-me stores email only; no password
  pre-fill; clear creds on sign-out / when remember-me is off.
- Match CSRF host lookup to OkHttp's host parsing; stop leaking raw exception text.

Correctness
- Fix API versioning: hardcode v1/v3 per endpoint (docs Sec.4) instead of one
  broken global apiVersion; remove the version plumbing + Settings field.
- Treat "warning" status as success (committed write); fail-fast on a missing
  pagination cursor; close Response on cancellation; tolerant JSON parse; User-Agent.
- Firmware isCompatible fails closed + extra acknowledgment for a non-compatible image.

Concurrency / lifecycle
- Run network I/O on Dispatchers.IO; stale-result generation guards + rethrow
  CancellationException in all loads; host AppState in a ViewModel (survive config
  change); thread-safe cookie jar; reset/upgrade re-entry guard; wire list Retry.

Build
- Enable R8 minify+shrink with kotlinx.serialization keep rules; drop unused
  navigation-compose; add the missing .gitignore.

NOTE: built/verified by static review only (no Android SDK on the dev machine) —
run :app:assembleDebug and a release build before shipping.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,25 @@
+# Gradle / build output
+.gradle/
+build/
+/app/build/
+
+# Local SDK / signing config and secrets (never commit)
+local.properties
+*.keystore
+*.jks
+keystore.properties
+signing.properties
+
+# Android Studio / IntelliJ
+.idea/
+*.iml
+captures/
+.externalNativeBuild/
+.cxx/
+
+# OS cruft
+.DS_Store
+Thumbs.db
+
+# Claude Code session state
+.claude/