infra: add Docker Compose setup for local development

- Configure PostgreSQL 18 and Valkey 9.1 services
- Create multi-stage Dockerfiles for API and Web apps
- Set up pnpm workspace support in container builds
- Configure hot reload via volume mounts for both services
- Add healthchecks for service orchestration
- Support dev/production stage targets (tsx watch vs compiled)

apps/web/Dockerfile

@@ -0,0 +1,19 @@
+# 1. Base
+FROM node:24-alpine AS base
+RUN npm install -g pnpm
+
+# 2. Deps
+FROM base AS deps
+WORKDIR /app
+COPY pnpm-lock.yaml pnpm-workspace.yaml package.json ./
+COPY apps/web/package.json ./apps/web/
+COPY packages/shared/package.json ./packages/shared/
+RUN pnpm install --frozen-lockfile
+
+# 3. Dev
+FROM base AS dev
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . ./
+EXPOSE 5173
+CMD ["pnpm", "--filter", "web", "dev", "--host"]