fix(docker): apply critical patches from third-party guide

Based on https://gist.github.com/PaulMColeman/e7ef82e05035b24300d2ea1954527f10

Changes:
- Add ca-certificates for rustup HTTPS downloads
- Install Rust and WASM toolchain for frontend WebAssembly compilation
- Copy config directory needed for FLUXER_CONFIG env var
- Set FLUXER_CONFIG so rspack can derive API endpoints
- Update ENTRYPOINT to target @fluxer/server package specifically
- Fix .dockerignore to allow build scripts and locale files

These fixes address the most critical build issues documented in the
community guide for self-hosting Fluxer.

fluxer_server/Dockerfile

@@ -11,6 +11,7 @@ RUN corepack enable && corepack prepare pnpm@10.26.0 --activate
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
 	curl \
+	ca-certificates \
 	python3 \
 	make \
 	g++ \
@@ -107,11 +108,20 @@ RUN LOGGER_LEVEL=${LOGGER_LEVEL} envsubst '${LOGGER_LEVEL}' < fluxer_gateway/con
 
 FROM deps AS app-build
 
+# Install Rust and WASM target for frontend WebAssembly compilation
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain stable
+ENV PATH="/root/.cargo/bin:${PATH}"
+RUN rustup target add wasm32-unknown-unknown
+
 COPY tsconfigs /usr/src/app/tsconfigs
+COPY config/ ./config/
 
 COPY packages/ ./packages/
 COPY fluxer_app/ ./fluxer_app/
 
+# Set FLUXER_CONFIG for rspack to derive API endpoints
+ENV FLUXER_CONFIG=/usr/src/app/config/config.production.template.json
+
 RUN cd fluxer_app && pnpm build
 
 FROM node:24-trixie-slim AS production
@@ -196,4 +206,5 @@ ENV RELEASE_CHANNEL=${RELEASE_CHANNEL}
 HEALTHCHECK --interval=30s --timeout=10s --retries=3 \
 	CMD curl -f http://localhost:8080/_health || exit 1
 
-ENTRYPOINT ["pnpm", "start"]
+# Target the fluxer_server package specifically
+ENTRYPOINT ["pnpm", "--filter", "@fluxer/server", "start"]