fix: dockerfiles build in compose context

- backend: copy dependency lockfiles from backend/ when build context is repo root
- frontend: don't copy public/ when it doesn't exist

backend/Dockerfile

@@ -20,7 +20,8 @@ ENV PATH="/root/.local/bin:${PATH}"
 FROM base AS deps
 
 # Copy only dependency metadata first for better build caching
-COPY pyproject.toml uv.lock ./
+# NOTE: compose builds backend with repo-root context, so files live under /backend.
+COPY backend/pyproject.toml backend/uv.lock ./
 
 # Create venv and sync deps (including runtime)
 RUN uv sync --frozen --no-dev

frontend/Dockerfile

@@ -28,7 +28,8 @@ ENV NODE_ENV=production
 ENV NEXT_PUBLIC_API_URL=http://localhost:8000
 
 COPY --from=builder /app/.next ./.next
-COPY --from=builder /app/public ./public
+# `public/` is optional in Next.js apps; repo may not have it.
+# Avoid failing the build when the directory is absent.
 COPY --from=builder /app/package.json ./package.json
 COPY --from=builder /app/node_modules ./node_modules
 COPY --from=builder /app/next.config.ts ./next.config.ts