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/api/Dockerfile

@@ -0,0 +1,42 @@
+# 1. select image and install pnpm
+FROM node:24-alpine AS base
+RUN npm install -g pnpm
+
+# 2. dependencies
+FROM base AS deps
+WORKDIR /app
+COPY pnpm-lock.yaml pnpm-workspace.yaml package.json ./
+COPY apps/api/package.json ./apps/api/
+COPY packages/shared/package.json ./packages/shared/
+COPY packages/db/package.json ./packages/db/
+RUN pnpm install --frozen-lockfile
+
+# 3. Development (only stage used)
+FROM base AS dev
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . ./
+EXPOSE 3000
+CMD ["pnpm", "--filter", "api", "dev"]
+
+# 4. build
+FROM base AS builder
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+RUN pnpm install
+RUN pnpm --filter shared build
+RUN pnpm --filter db build
+RUN pnpm --filter api build
+
+# 5. run
+FROM base AS runner
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY --from=deps /app/packages/shared/package.json /app/packages/shared/package.json
+COPY --from=deps /app/packages/db/package.json /app/packages/db/package.json
+COPY --from=builder /app/apps/api/dist ./dist
+COPY --from=builder /app/packages/shared/dist /app/packages/shared/dist
+COPY --from=builder /app/packages/db/dist /app/packages/db/dist
+EXPOSE 3000
+CMD ["node", "dist/server.js"]