fix(deps): pin livekit family to versions matching EC-compat fork proto schema

Newer livekit-rtc releases added a ParticipantState symbol to
participant_pb2 that the EC-compat Rust fork (onestacked/livekit-rust-sdks
branch EC-compat-changes, PR #904) doesnt regenerate. The Dockerfile
overwrites the pip-installed protos with the forks regen output, so
patch_sdk.py crashed on "import livekit.rtc" with:
  ImportError: cannot import name ParticipantState from livekit.rtc._proto.participant_pb2

Pinned to the versions running in the last successful image (build of
2026-04-03):
  livekit==1.1.3 livekit-api==1.1.0 livekit-agents==1.5.1
  livekit-plugins-{openai,elevenlabs,silero}==1.5.1

Build verified locally: docker compose build bot exits 0; patch_sdk
applies cleanly; bot starts, syncs, /health returns ok.

requirements.txt

@@ -1,9 +1,9 @@
-livekit-agents>=1.4,<2.0
+livekit-agents==1.5.1
-livekit-plugins-openai>=1.4,<2.0
+livekit-plugins-openai==1.5.1
-livekit-plugins-elevenlabs>=1.4,<2.0
+livekit-plugins-elevenlabs==1.5.1
-livekit-plugins-silero>=1.4,<2.0
+livekit-plugins-silero==1.5.1
-livekit>=1.0,<2.0
+livekit==1.1.3
-livekit-api>=1.0,<2.0
+livekit-api==1.1.0
 matrix-nio[e2e]>=0.25,<1.0
 canonicaljson>=2.0,<3.0
 httpx>=0.27,<1.0