Improve developer integration docs and Docker dev workflow.

Add TypeScript frontend integration documentation, repository agent guidance files, Go-served frontend routing, and an advanced Docker Compose setup with watch mode plus BuildKit cache configuration.

Made-with: Cursor

Dockerfile

@@ -1,6 +1,6 @@
 # syntax=docker/dockerfile:1.7
 
-FROM --platform=$BUILDPLATFORM golang:1.25-bookworm AS builder
+FROM --platform=$BUILDPLATFORM golang:1.25-bookworm AS base
 
 ARG TARGETOS
 ARG TARGETARCH
@@ -15,12 +15,19 @@ RUN --mount=type=cache,target=/go/pkg/mod \
     go mod download
 
 COPY . .
+
+FROM base AS builder
 RUN --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
     CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} \
     go build -p "$(nproc)" -trimpath -ldflags="-s -w" -o /out/api ./cmd/api
 
-FROM gcr.io/distroless/static-debian12:nonroot
+FROM base AS dev
+ENV ADDR=:8080
+EXPOSE 8080
+CMD ["go", "run", "./cmd/api"]
+
+FROM gcr.io/distroless/static-debian12:nonroot AS runtime
 
 WORKDIR /app
 COPY --from=builder /out/api /app/api