feat: add Docker support with self-hosted and hosted presets

Multi-stage Dockerfile (Node 22 Alpine), docker-compose for self-hosted
and hosted deployments, CI workflow for GHCR publishing, runtime env var
substitution, and cron sidecar with supercronic.

Aligns hosted extension preset with dev config (enable-banking,
ai-categorization, ai-chat, email).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-entrypoint.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# Replace build-time placeholder sentinels with runtime env vars in static JS bundles.
+# This allows a single pre-built image to work with any Supabase project.
+if [ -d /app/.next/static ]; then
+  find /app/.next/static -name '*.js' -exec sed -i \
+    -e "s|__NEXT_PUBLIC_SUPABASE_URL__|${NEXT_PUBLIC_SUPABASE_URL}|g" \
+    -e "s|__NEXT_PUBLIC_SUPABASE_ANON_KEY__|${NEXT_PUBLIC_SUPABASE_ANON_KEY}|g" \
+    -e "s|__NEXT_PUBLIC_APP_URL__|${NEXT_PUBLIC_APP_URL}|g" \
+    -e "s|__NEXT_PUBLIC_VAPID_PUBLIC_KEY__|${NEXT_PUBLIC_VAPID_PUBLIC_KEY:-}|g" \
+    {} +
+fi
+
+exec "$@"