feat: Added nix flake for build.

Dockerfile

@@ -6,16 +6,12 @@ RUN apk add --no-cache \
     curl-dev \
     libxml2-dev \
     openssl-dev \
-    git \
     pkgconf
 
 WORKDIR /app
 COPY . /app
 
-RUN git clone https://git.bwaaa.monster/beaker /tmp/beaker && \
-    cd /tmp/beaker && \
-    make && make install && \
-    rm -rf /tmp/beaker
+RUN make -C vendor/beaker && make -C vendor/beaker install
 
 RUN make clean && make && strip bin/omnisearch