feat(docker): add containerized nginx deployment with runtime base path

Two-stage build: node builds the static bundle, nginx serves it. The bundle is
built against a placeholder base token that the entrypoint rewrites to $BASE_URL
at start, so one image serves from any path without a rebuild.

nginx config caches hashed assets forever, never caches index.html, and applies
security headers (CSP, no framing, no referrer) suited to an app that handles
cloud credentials client-side.

.gitattributes pins LF on the container-consumed files, since core.autocrlf
would otherwise give the entrypoint a CRLF shebang.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docker/40-ready2blob-base-url.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+# Applies $BASE_URL to the built bundle and the nginx config at container start.
+#
+# The bundle is built with Vite's base set to the literal token below, so every asset
+# URL in the emitted HTML/JS/CSS carries it. Rewriting that token here is what lets one
+# image serve from any path without a rebuild.
+set -eu
+
+TOKEN='/__R2B_BASE__/'
+SRC='/opt/ready2blob/html'
+DEST='/usr/share/nginx/html'
+
+# Normalize to a leading and trailing slash: "app" and "/app" both mean "/app/".
+base="${BASE_URL:-/}"
+case "$base" in /*) ;; *) base="/$base" ;; esac
+case "$base" in */) ;; *) base="$base/" ;; esac
+
+echo "ready2blob: serving from base $base"
+
+# Rebuild the web root from the pristine copy on every start, so both restarts and
+# BASE_URL changes are idempotent.
+rm -rf "${DEST:?}"/*
+mkdir -p "$DEST$base"
+cp -R "$SRC/." "$DEST$base"
+
+# '|' as the sed delimiter, since both needle and replacement contain '/'.
+find "$DEST" -type f \( -name '*.html' -o -name '*.js' -o -name '*.css' \) \
+    -exec sed -i "s|$TOKEN|$base|g" {} +
+
+# Restrict envsubst to BASE_URL so nginx's own $uri / $1 survive untouched.
+export BASE_URL="$base"
+envsubst '${BASE_URL}' \
+    < /etc/nginx/ready2blob.conf.template \
+    > /etc/nginx/conf.d/default.conf

docker/nginx.conf.template

@@ -0,0 +1,33 @@
+# Rendered to /etc/nginx/conf.d/default.conf at startup, with ${BASE_URL} substituted.
+# See docker/40-ready2blob-base-url.sh.
+server {
+    listen      80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+
+    include /etc/nginx/snippets/security-headers.conf;
+
+    gzip            on;
+    gzip_vary       on;
+    gzip_min_length 1024;
+    gzip_types      text/css application/javascript image/svg+xml application/json;
+
+    # Vite emits content-hashed filenames under assets/ — safe to cache forever.
+    location ${BASE_URL}assets/ {
+        include /etc/nginx/snippets/security-headers.conf;
+        add_header Cache-Control "public, max-age=31536000, immutable" always;
+    }
+
+    # index.html must never be cached, or clients pin to a stale bundle after a redeploy.
+    location = ${BASE_URL}index.html {
+        include /etc/nginx/snippets/security-headers.conf;
+        add_header Cache-Control "no-cache" always;
+    }
+
+    # No `$uri/` here on purpose: if the directory exists but holds no index file,
+    # nginx answers 403 instead of falling through to the fallback.
+    location / {
+        try_files $uri ${BASE_URL}index.html;
+    }
+}

docker/security-headers.conf

@@ -0,0 +1,15 @@
+# Ready2Blob handles cloud credentials in the browser and sends them nowhere.
+# These headers keep it that way: no framing, no external origins, no referrer leakage.
+#
+# Included per-location as well as at server level on purpose: an `add_header` inside
+# a location block REPLACES every header inherited from the parent, so any location
+# that sets its own Cache-Control must re-include this file.
+add_header X-Content-Type-Options "nosniff" always;
+add_header X-Frame-Options        "DENY" always;
+add_header Referrer-Policy        "no-referrer" always;
+add_header Permissions-Policy     "geolocation=(), camera=(), microphone=(), usb=()" always;
+
+# script-src keeps 'unsafe-inline' for the theme/FOUC bootstrap in index.html.
+# To tighten it: build once, read the emitted inline <script> from dist/index.html,
+# and swap 'unsafe-inline' for its 'sha256-...' hash.
+add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; connect-src 'self'; form-action 'none'; frame-ancestors 'none'; base-uri 'self'; object-src 'none'" always;