Add Ulfius: C REST framework on GNU Libmicrohttpd (first C app framework!)

frameworks/ulfius/Dockerfile

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+FROM ubuntu:24.04 AS build
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    gcc make cmake git ca-certificates pkg-config \
+    libmicrohttpd-dev libjansson-dev libcurl4-openssl-dev \
+    libgnutls28-dev libsqlite3-dev zlib1g-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Build ulfius and its dependency orcania/yder from source
+WORKDIR /tmp
+RUN git clone --depth 1 --branch v2.3.3 https://github.com/babelouest/orcania.git && \
+    cd orcania && cmake -B build -DCMAKE_BUILD_TYPE=Release -S . && \
+    cmake --build build -j$(nproc) && cmake --install build
+
+RUN git clone --depth 1 --branch v1.4.20 https://github.com/babelouest/yder.git && \
+    cd yder && cmake -B build -DCMAKE_BUILD_TYPE=Release -DWITH_JOURNALD=OFF -S . && \
+    cmake --build build -j$(nproc) && cmake --install build
+
+RUN git clone --depth 1 --branch v2.7.15 https://github.com/babelouest/ulfius.git && \
+    cd ulfius && cmake -B build -DCMAKE_BUILD_TYPE=Release \
+      -DWITH_WEBSOCKET=OFF -DWITH_CURL=OFF \
+      -DCMAKE_C_FLAGS="-O3 -flto" \
+      -S . && \
+    cmake --build build -j$(nproc) && cmake --install build
+
+RUN ldconfig
+
+# Build our server
+WORKDIR /app
+COPY src/server.c ./
+RUN gcc -O3 -flto -march=native -o server server.c \
+    $(pkg-config --cflags --libs libulfius) \
+    -ljansson -lsqlite3 -lz -lm -lpthread
+
+FROM ubuntu:24.04
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libmicrohttpd12t64 libjansson4 libgnutls30t64 libsqlite3-0 zlib1g && \
+    rm -rf /var/lib/apt/lists/*
+COPY --from=build /usr/local/lib/libulfius.so* /usr/local/lib/
+COPY --from=build /usr/local/lib/liborcania.so* /usr/local/lib/
+COPY --from=build /usr/local/lib/libyder.so* /usr/local/lib/
+COPY --from=build /app/server /server
+RUN ldconfig
+
+EXPOSE 8080 8443
+CMD ["/server"]

frameworks/ulfius/README.md

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+# Ulfius — C REST Framework
+
+[Ulfius](https://github.com/babelouest/ulfius) is a lightweight HTTP framework for building REST APIs in pure C. Built on GNU Libmicrohttpd with Jansson for JSON processing, it's designed for embedded systems and applications where a small memory footprint matters.
+
+## Why it's interesting
+
+- **Pure C** — first C application framework in HttpArena (h2o/nginx are web servers, not app frameworks)
+- **Libmicrohttpd backend** — battle-tested GNU HTTP library under the hood
+- **Minimal footprint** — designed for embedded/constrained environments
+- **Solo developer project** — @babelouest has been maintaining this since 2015
+
+## Implementation notes
+
+- Uses Jansson for all JSON serialization (same lib used by many C projects)
+- Thread-local SQLite connections with prepared statements for `/db`
+- Pre-loads datasets and static files into memory at startup
+- TLS via GnuTLS (Ulfius's built-in secure framework support)
+- Signal-based clean shutdown

frameworks/ulfius/meta.json

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+{
+  "display_name": "ulfius",
+  "language": "C",
+  "type": "framework",
+  "engine": "libmicrohttpd",
+  "description": "Ulfius C REST framework built on GNU Libmicrohttpd with Jansson JSON. Lightweight with small memory footprint, designed for embedded systems.",
+  "repo": "https://github.com/babelouest/ulfius",
+  "enabled": true,
+  "tests": [
+    "baseline",
+    "noisy",
+    "pipelined",
+    "limited-conn",
+    "json",
+    "upload",
+    "compression",
+    "mixed"
+  ]
+}