perf: docker + next.js build optimisation - dockerignore exclusions, BuildKit cache mounts, backend image reuse, memory limits, next.js bundle tree-shaking

backend/Dockerfile.dev

@@ -1,14 +1,28 @@
+# ═══════════════════════════════════════════════════════════════════════════
+#  PragatiVeer Backend – Python 3.11 slim
+#  Optimised for fast re-builds:
+#    • requirements.txt copied FIRST → pip cache layer is only invalidated
+#      when dependencies change, not on every source-code edit.
+#    • BuildKit pip cache mount keeps wheel cache on host between builds.
+# ═══════════════════════════════════════════════════════════════════════════
 FROM python:3.11-slim
 
+# Install system deps in a single RUN layer, clean apt cache immediately
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        build-essential \
+        libpq-dev \
+    && rm -rf /var/lib/apt/lists/*
+
 WORKDIR /app
 
-RUN apt-get update && apt-get install -y \
-    build-essential \
-    libpq-dev \
-    && rm -rf /var/lib/apt/lists/*
-
+# ── Dependencies first (most stable layer) ──────────────────────────────────
 COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+# Use BuildKit pip cache so wheels are reused across builds
+RUN --mount=type=cache,target=/root/.cache/pip \
+    pip install --no-cache-dir -r requirements.txt
+
+# ── Source code (changes frequently; comes last) ─────────────────────────────
+COPY . .
 
 EXPOSE 8000