fix: instructor hooks crash + Dockerfile lockfile for consistent builds

- Fix on_completion_kwargs handler to accept **kwargs (instructor now
  passes messages, model, etc. as individual keyword args, not a dict)
- Copy uv.lock into Docker image so builds use locked versions instead
  of re-resolving, which could install incompatible versions

Author: iamjr15

backend/Dockerfile

@@ -9,9 +9,8 @@ RUN apk add --no-cache curl git
 RUN addgroup -g 1001 app && adduser -D -G app -u 1001 app
 
 # Install Python dependencies
-COPY pyproject.toml ./
+COPY pyproject.toml uv.lock ./
 ENV UV_LINK_MODE=copy
-RUN --mount=type=cache,target=/root/.cache/uv uv lock
 RUN --mount=type=cache,target=/root/.cache/uv uv sync --locked --quiet
 
 # Fix ownership of the entire /app directory including .venv

backend/services/structured_llm.py

@@ -37,7 +37,7 @@ def _register_hooks(client: instructor.AsyncInstructor) -> None:
     catching events that manual logging at the call site would miss.
     """
 
-    def on_completion_kwargs(kwargs: dict[str, Any]) -> None:
+    def on_completion_kwargs(**kwargs: Any) -> None:
         logger.info(
             "Structured LLM request",
             model=kwargs.get("model", "unknown"),