feat: Update Dockerfile to include libc6-dev and version 1.4.0, and add backend/requirements.txt for dependencies.

Dockerfile

@@ -3,7 +3,7 @@
 FROM python:3.11-slim AS builder
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends gcc libffi-dev \
+    && apt-get install -y --no-install-recommends gcc libffi-dev libc6-dev \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /build
@@ -14,7 +14,7 @@ RUN pip install --no-cache-dir --prefix=/install -r requirements.txt
 FROM python:3.11-slim
 
 LABEL maintainer="Bruno Beloeil" \
-      version="1.3.0" \
+      version="1.4.0" \
       description="ObsiGate — lightweight web interface for Obsidian vaults"
 
 WORKDIR /app