fix(sonar): compare speed with math.isclose instead of float equality (python:S1244)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

routes/tts.py

@@ -7,6 +7,7 @@ import io
 import json
 import logging
 import hashlib
+import math
 import os
 import re
 import threading
@@ -805,7 +806,7 @@ async def tts_preview(request: Request):
     if _speed_v is not None and _speed_v != "":
         try:
             _speed_f = float(_speed_v)
-            if _speed_f != 1.0:
+            if not math.isclose(_speed_f, 1.0):
                 _overrides["speed"] = max(0.1, min(4.0, _speed_f))
         except (TypeError, ValueError):
             pass