Refactor Dockerfile and add fit_model functionality

- Updated the Dockerfile to rename the built binary from `mf-fitter` to `fit_model` for clarity.
- Introduced a new `fit_model_args.rs` file to define command-line arguments for the fit model process, including parameters for matrix factorization.
- Added `pg_types.rs` and `pgvector.rs` files to handle PostgreSQL type interactions and vector serialization/deserialization.
- Implemented the main logic for the fit model in `fit_model.rs`, including data loading, model training, and embedding saving.
- Enhanced `visualize_embeddings.rs` to load embeddings and clusters more efficiently.

These changes improve the organization and functionality of the model fitting process, making it more intuitive and maintainable.

Dockerfile

@@ -32,7 +32,7 @@ COPY . .
 RUN --mount=type=cache,target=/usr/local/cargo/registry \
     --mount=type=cache,target=/app/target \
     cargo build --release && \
-    cp target/release/mf-fitter /app/mf-fitter
+    cp target/release/fit_model /app/fit_model
 
 # Create the runtime image
 FROM debian:bullseye-slim
@@ -48,7 +48,7 @@ RUN apt-get update && \
         && rm -rf /var/lib/apt/lists/*
 
 # Copy the binary from builder
-COPY --from=builder /app/mf-fitter /usr/local/bin/
+COPY --from=builder /app/fit_model /usr/local/bin/
 COPY --from=builder /app/.env.example /app/.env
 
 WORKDIR /app
@@ -56,4 +56,4 @@ WORKDIR /app
 # Set environment variables
 ENV RUST_LOG=info
 
-ENTRYPOINT ["/usr/local/bin/mf-fitter"]
+ENTRYPOINT ["/usr/local/bin/fit_model"]