docs: Add 6, update 4 and remove 2 files

Dockerfile.dropshell-build

@@ -0,0 +1,57 @@
+ARG IMAGE_TAG
+FROM gitea.jde.nz/public/dropshell-build-base:latest AS builder
+
+ARG PROJECT=dropshell
+ARG CMAKE_BUILD_TYPE=Debug
+
+# Set working directory
+WORKDIR /app
+
+# Create cache directories
+RUN mkdir -p /ccache
+
+# Set up ccache
+ENV CCACHE_DIR=/ccache
+ENV CCACHE_COMPILERCHECK=content
+ENV CCACHE_MAXSIZE=2G
+
+# Copy source files and build scripts
+COPY source/src/ src/
+COPY source/agent-local/ agent-local/
+COPY source/agent-remote/ agent-remote/
+COPY source/CMakeLists.txt ./
+COPY source/cmake_prebuild.sh ./
+
+# Configure project (this step is cached unless CMakeLists.txt changes)
+RUN --mount=type=cache,target=/ccache \
+    --mount=type=cache,target=/build \
+    mkdir -p /build && \
+    cmake -G Ninja -S /app -B /build \
+    -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} \
+    -DCMAKE_CXX_COMPILER_LAUNCHER=ccache \
+    -DCMAKE_C_COMPILER_LAUNCHER=ccache \
+    -DCMAKE_EXE_LINKER_FLAGS="-fuse-ld=mold -static -g" \
+    -DCMAKE_CXX_FLAGS="-g -fno-omit-frame-pointer" \
+    -DCMAKE_C_FLAGS="-g -fno-omit-frame-pointer" \
+    -DPROJECT_NAME="${PROJECT}" \
+    -DCMAKE_STRIP=OFF \
+    ${CMAKE_TOOLCHAIN_FILE:+-DCMAKE_TOOLCHAIN_FILE=$CMAKE_TOOLCHAIN_FILE}
+
+# Build project (ccache will help here when only some files change)
+RUN --mount=type=cache,target=/ccache \
+    --mount=type=cache,target=/build \
+    cmake --build /build
+
+# Copy the built executables to a regular directory for the final stage
+RUN --mount=type=cache,target=/build \
+    mkdir -p /output && \
+    find /build -type f -executable -name "*${PROJECT}*" -exec cp {} /output/${PROJECT} \; || \
+    find /build -type f -executable -exec cp {} /output/${PROJECT} \;
+
+# Final stage that only contains the binaries
+FROM scratch AS project
+
+ARG PROJECT=dropshell
+
+# Copy the actual binaries from the regular directory
+COPY --from=builder /output/${PROJECT} /${PROJECT}