feat: switch email delivery from Resend to SMTP with libcurl integration

Dockerfile

@@ -6,7 +6,7 @@ ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     build-essential ccache cmake ninja-build git pkg-config \
-    libssl-dev zlib1g-dev \
+    libcurl4-openssl-dev libssl-dev zlib1g-dev \
     libmariadb-dev libmariadb-dev-compat \
     libsqlite3-dev python3 libjsoncpp-dev uuid-dev ca-certificates \
     && rm -rf /var/lib/apt/lists/*
@@ -27,7 +27,7 @@ FROM ubuntu:22.04 AS runtime
 ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    libssl3 ca-certificates libstdc++6 libmariadb3 libjsoncpp25 libuuid1 \
+    libcurl4 libssl3 ca-certificates libstdc++6 libmariadb3 libjsoncpp25 libuuid1 \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app