V45: D17 seamless loop wrap + D18 stop solo note-off (Qin) + D18b/c guard + engine VST load fixes

- D17: wrap_info/wrap-skip, fx wrap xfade, playhead-derived scheduling
- D18: solo stop -> NOTE_OFF all sounding timeline pitches + CC123/CC120
- D18b: track audible gain guard, tracksRef fallback
- D18c: timelinePitchesRef per-track Set, kill at applyAllTrackMuteSolo
- bridge ring _MAX 16, index v=202608290928
- plugins.py/vst_engine.py/fx_realtime.py/JuceFxEngine.cpp: VSTi load + Qin fixes (uncommitted 12:18)

app/core/fx_realtime.py

@@ -23,10 +23,7 @@ import threading
 import time
 import uuid
 
-import numpy as np
-
 from app.config import settings
-from app.core.native_render import find_fx_bridge_exe, find_juce_fx_bridge_exe
 
 FXRT_MAGIC = 0x46585254
 FXRT_BLOCK = 256
@@ -91,6 +88,7 @@ class FxRealtimeSession:
     """Một session realtime: SHM + subprocess fx_vst_bridge + I/O block."""
 
     def __init__(self, fx_chain, sample_rate, block_size=FXRT_BLOCK):
+        import numpy as np
         from multiprocessing import shared_memory
         self.fx_chain = fx_chain or []
         self.sample_rate = int(sample_rate)
@@ -163,6 +161,7 @@ class FxRealtimeSession:
         return out
 
     def _spawn(self):
+        from app.core.native_render import find_fx_bridge_exe, find_juce_fx_bridge_exe
         juce_exe = os.getenv("SF_JUCE_FX_BRIDGE_PATH", "").strip()
         # G3: mặc định dùng JUCE bridge (latency graph thật + processed samples);
         # fallback bridge cũ khi không có exe JUCE (regression an toàn).
@@ -265,6 +264,7 @@ class FxRealtimeSession:
         """Gom FXRT_IN_SLOTS frame vào pending, đủ 4 → publish atomic vào ring
         (ghi data toàn bộ slot trước, sau đó in_write += n 1 lần). Ring đầy khi
         publish → drop batch cũ nhất (giữ latency thấp)."""
+        import numpy as np
         arr = np.frombuffer(interleaved, dtype=np.float32)
         if arr.size != self.block_size * 2:
             return
@@ -333,6 +333,7 @@ class FxRealtimeSession:
             self.stats['flush'] += 1
 
     def read_output(self):
+        import numpy as np
         """Drain output ring → list bytes (mỗi block 2048 bytes interleaved)."""
         out = []
         with self._lock: