feat(dashboard): conversation log filter by time/user/server/channel/content

Adds the requested multi-dimension log search. Turns now carry speaker, guild
and channel (the bot sends X-User/Guild/Channel-Name on the voice-turn POST), and
a filter bar above the conversation feed narrows by 시간(최근 N분)·유저·서버·
채널·내용. The event/error panel keeps its text+level search.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

wsai/monitor.py

@@ -81,6 +81,8 @@ class Turn:
         self.id = turn_id
         self.source = source
         self.speaker = ""  # who spoke (Discord display name), when known
+        self.guild = ""    # server name, when known (for 서버별 필터)
+        self.channel = ""  # voice channel name, when known (for 채널별 필터)
         self.wall = _now_wall()
         self._t0 = _now_mono()
         self.heard_text = ""
@@ -139,6 +141,8 @@ class Turn:
             "id": self.id,
             "source": self.source,
             "speaker": self.speaker,
+            "guild": self.guild,
+            "channel": self.channel,
             "wall": self.wall,
             "heard": self.heard_text,
             "thought": self.thought_text,