feat(streamhub): parse +Recorder config and add recorder WS commands

Parse the optional +Recorder block in Initialise (Enabled/AutoStart/
Directory/MaxFileMB/KeepFiles/StagingMB/FlushIntervalSec/MinDiskFreeMB/
Signals, MB->bytes), apply it to each session before Start (static and
dynamic sources). Drive recorder disk I/O from the push loop via
RecorderFlushTick, and add recStart/recStop/recInfo WS commands plus a
recStatus broadcast/snapshot.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Source/Applications/StreamHub/StreamHub.h

@@ -146,6 +146,20 @@ private:
     void HandleSetMaxPoints(const char *json);
     void HandlePing(uint32 slotIdx);
 
+    /* ---- Binary recorder commands --------------------------------------- */
+
+    /** Arm recording on all enabled sessions (optional "sourceId" filter). */
+    void HandleRecStart(const char *json);
+    /** Disarm recording on all enabled sessions (optional "sourceId" filter). */
+    void HandleRecStop(const char *json);
+    /** Unicast a {"type":"recStatus",...} snapshot to one client. */
+    void HandleRecInfo(uint32 slotIdx);
+    /** Broadcast a {"type":"recStatus",...} snapshot to all clients. */
+    void BroadcastRecStatus();
+
+    /** Append the full recStatus message body into a growable buffer. */
+    void AppendRecStatusJSON(char *&buf, uint32 &off, uint32 &cap);
+
     /* ---- Sources persistence (Go SourceConfig schema) --------------------- */
 
     /**
@@ -191,6 +205,9 @@ private:
     TriggerEngine     trigger_;
     HistoryWriter     history_;
 
+    /* Recorder configuration (parsed once, applied to each session). */
+    RecorderConfig    recorderCfg_;
+
     /* Configuration */
     uint16  wsPort_;
     uint32  maxPoints_;