feat: refine dockerfile to deploy on host service provider

.dockerignore

@@ -23,3 +23,24 @@ test/
 integration_test/
 coverage/
 custom_lint.log
+test_cache/
+unit_test_assets/
+
+# Docs and repo meta to avoid cache busting
+docs/
+**/*.md
+wireframe.assets/
+AGENTS.md
+README.md
+LICENSE
+
+# Packaging artifacts not needed for web image
+AppDir/
+AppRun
+pdf_signature.desktop
+tool/
+*.iml
+*.ipr
+*.iws
+.github/
+.husky/

Dockerfile

@@ -1,3 +1,4 @@
+# syntax=docker/dockerfile:1.7-labs
 ## Two-stage build for minimal Flutter web static server (Caddy runtime)
 # Stage 1: Build the Flutter web app
 FROM ghcr.io/cirruslabs/flutter:latest AS build
@@ -6,13 +7,17 @@ WORKDIR /app
 
 # Copy pubspec first for better layer caching
 COPY pubspec.* ./
-RUN flutter pub get
+# Use BuildKit cache for Dart pub cache
+RUN --mount=type=cache,target=/root/.pub-cache \
+	flutter pub get
 
 # Copy the rest of the project
 COPY . .
 
-# Ensure no host caches leak into the container
+# Ensure no host caches leak into the container; use BuildKit caches for pub and Flutter
-RUN rm -rf .dart_tool build && \
+RUN --mount=type=cache,target=/root/.pub-cache \
+    --mount=type=cache,target=/sdks/flutter/bin/cache \
+    rm -rf .dart_tool build && \
 	flutter pub get && \
 	flutter gen-l10n && \
 	flutter build web --release -O4 --wasm
@@ -23,12 +28,13 @@ WORKDIR /usr/share/caddy
 # Copy built web assets
 COPY --from=build /app/build/web/ /usr/share/caddy/
 # Write Caddyfile inline (listens on :8080 and SPA fallback)
+ENV PORT=8080
 RUN cat > /etc/caddy/Caddyfile <<'CADDY'
 {
 	admin off
 }
 
-:8080 {
+:{$PORT} {
 	root * /usr/share/caddy
 	encode zstd gzip
 	# SPA fallback: serve index.html if file not found
@@ -36,4 +42,13 @@ RUN cat > /etc/caddy/Caddyfile <<'CADDY'
 	file_server
 }
 CADDY
+# Some platforms (e.g., gVisor/Firecracker like Render) forbid file capabilities; strip and copy to a clean path
+USER root
+RUN apk add --no-cache libcap && \
+	(setcap -r /usr/bin/caddy || true) && \
+	install -m 0755 /usr/bin/caddy /caddy && \
+	apk del libcap
+# Use numeric UID/GID for caddy to avoid passwd lookup issues across platforms
+USER 65532:65532
 EXPOSE 8080
+ENTRYPOINT ["/caddy", "run", "--config", "/etc/caddy/Caddyfile", "--adapter", "caddyfile"]