fix: macOS block index corruption, dbcache auto-sizing, import key rescan height

- Shutdown: 3-phase stop (wait for RPC stop → SIGTERM → SIGKILL) prevents
  LevelDB flush interruption on macOS/APFS that caused full re-sync on restart
- dbcache: auto-detect RAM and set -dbcache to 12.5% (clamped 450-4096 MB)
  on macOS (sysctl), Linux (sysconf), and Windows (GlobalMemoryStatusEx)
- Import key: pass user-entered start height to z_importkey and trigger
  rescanblockchain from that height for t-key imports
- Bump version to 1.1.1

src/config/version.h

@@ -7,10 +7,10 @@
 // !! DO NOT EDIT version.h — it is generated from version.h.in by CMake.
 // !! Change the version in CMakeLists.txt: project(... VERSION x.y.z ...)
 
-#define DRAGONX_VERSION "1.1.0"
+#define DRAGONX_VERSION "1.1.1"
 #define DRAGONX_VERSION_MAJOR 1
 #define DRAGONX_VERSION_MINOR 1
-#define DRAGONX_VERSION_PATCH 0
+#define DRAGONX_VERSION_PATCH 1
 
 #define DRAGONX_APP_NAME "ObsidianDragon"
 #define DRAGONX_ORG_NAME "Hush"