Release: NX9-Auth v0.3.0

RELEASE_NOTES.md

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+# NX9-Auth v0.3.0 Release Notes
+
+NX9-Auth v0.3.0 brings full architectural stabilization, unified runtime lifecycle management, and production-grade operational robustness to self-hosted Identity and Access Management.
+
+## Key Features & Highlights
+
+### ⚡ Unified Modular Runtime Subsystem
+- **Application Container & Builder**: Pure dependency assembly separating configuration, database provider initializations, repository traits, and router construction.
+- **Lock-Free State Machine**: `AtomicRuntimeState` tracks granular lifecycle states without mutex contention.
+- **Signal Handling & Cancellation**: Multi-signal Unix signal manager handling `SIGINT` (Ctrl+C) and `SIGTERM` with parent-child cancellation tokens.
+
+### 🛡️ Operational Stability & Graceful Shutdown
+- **Orderly Shutdown Flow**: `Running` -> `Draining` -> `StoppingWorkers` -> `ExecutingHooks` -> `ClosingResources` -> `Stopped`.
+- **Prioritized Hook Execution**: Supports custom shutdown hooks executed in priority order with error isolation.
+- **Background Worker Management**: `WorkerManager` manages background task groups with configurable timeout cancellation.
+
+### 🗄️ Dual-Database Engine Support
+- Native support for SQLite (WAL mode, foreign keys, busy timeout) and PostgreSQL with automatic migrations and robust connection retry policies.
+
+### 🚀 Developer & Operator Experience
+- Built-in single binary execution (`nx9-auth serve`).
+- Diagnostic `nx9-auth doctor` command for environment verification.
+- Full Admin SPA UI shell embedded directly in the single binary.