docs: update README project structure and Dockerfile description

- Remove web/dist/ individual files from project structure (now generated
  at Docker build time, not committed)
- Add web/src/, build.sh, package.json, package-lock.json to structure
- Update Dockerfile description from two-stage to four-stage build
  (web-builder, lint, builder, final)
- Remove outdated example Dockerfile snippet

README.md

@@ -1850,26 +1850,14 @@ docker run -p 8080:8080 \
   neoirc
 ```
 
-The Dockerfile is a multi-stage build:
-1. **Build stage**: Compiles `neoircd` and `neoirc-cli` (CLI built to verify
-   compilation, not included in final image)
-2. **Final stage**: Alpine Linux + `neoircd` binary only
-
-```dockerfile
-FROM golang:1.24-alpine AS builder
-WORKDIR /src
-RUN apk add --no-cache make
-COPY go.mod go.sum ./
-RUN go mod download
-COPY . .
-RUN go build -o /neoircd ./cmd/neoircd/
-RUN go build -o /neoirc-cli ./cmd/neoirc-cli/
-
-FROM alpine:latest
-COPY --from=builder /neoircd /usr/local/bin/neoircd
-EXPOSE 8080
-CMD ["neoircd"]
-```
+The Dockerfile is a four-stage build:
+1. **web-builder**: Installs Node dependencies and compiles the SPA (JSX →
+   bundled JS via esbuild) into `web/dist/`
+2. **lint**: Runs formatting checks and golangci-lint against the Go source
+   (with the built SPA assets copied in)
+3. **builder**: Runs tests and compiles static `neoircd` and `neoirc-cli`
+   binaries (CLI built to verify compilation, not included in final image)
+4. **final**: Minimal Alpine image with only the `neoircd` binary
 
 ### Binary
 
@@ -2318,10 +2306,14 @@ neoirc/
 │       └── http.go         # HTTP timeouts
 ├── web/
 │   ├── embed.go            # go:embed directive for SPA
-│   └── dist/               # Built SPA (vanilla JS, no build step)
-│       ├── index.html
-│       ├── style.css
-│       └── app.js
+│   ├── build.sh            # SPA build script (esbuild, runs in Docker)
+│   ├── package.json        # Node dependencies (preact, esbuild)
+│   ├── package-lock.json
+│   ├── src/                # SPA source files (JSX + HTML + CSS)
+│   │   ├── app.jsx
+│   │   ├── index.html
+│   │   └── style.css
+│   └── dist/               # Generated at Docker build time (not committed)
 ├── schema/                 # JSON Schema definitions (planned)
 ├── go.mod
 ├── go.sum