Add read-only web UI

Serves Pete's classified-story archive over HTTP alongside the Matrix
bot. Three sections (gaming/tech/politics), Animal-Crossing-vibe Tailwind
templates, day/night palette driven by the visitor's browser clock.
Web port configurable via web.listen_addr and ${PETE_WEB_PORT} in
docker-compose. Tailwind built in a node stage in the Dockerfile so
deployments don't need node at runtime.

internal/web/server.go

@@ -0,0 +1,104 @@
+// Package web serves Pete's read-only news interface.
+package web
+
+import (
+	"context"
+	"embed"
+	"errors"
+	"html/template"
+	"io/fs"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"pete/internal/config"
+)
+
+//go:embed templates/*.html
+var templateFS embed.FS
+
+//go:embed static
+var staticFS embed.FS
+
+// Channel describes one section of the site.
+type Channel struct {
+	Slug  string // "gaming"
+	Title string // "Gaming"
+	Theme string // tailwind theme key: "gaming" | "tech" | "politics"
+	Emoji string
+	Blurb string
+}
+
+// channels in display order. Add a new entry here to add a section.
+var channels = []Channel{
+	{Slug: "gaming", Title: "Gaming", Theme: "gaming", Emoji: "🎮", Blurb: "Releases, platforms, and the people making the games."},
+	{Slug: "tech", Title: "Tech", Theme: "tech", Emoji: "💻", Blurb: "Industry, products, and the wires that hold it all together."},
+	{Slug: "politics", Title: "Politics", Theme: "politics", Emoji: "🏛️", Blurb: "Policy, power, and the news of the day."},
+}
+
+// Server is the HTTP server for Pete's web UI.
+type Server struct {
+	cfg  config.WebConfig
+	srv  *http.Server
+	tpls map[string]*template.Template // keyed by page name (e.g. "index", "channel")
+}
+
+// New builds the server. Templates are parsed once at startup. Each page
+// gets its own template set sharing layout.html + _card.html, which avoids
+// `main` define collisions between pages.
+func New(cfg config.WebConfig) (*Server, error) {
+	pages := []string{"index", "channel"}
+	tpls := make(map[string]*template.Template, len(pages))
+	for _, p := range pages {
+		t, err := template.New("").Funcs(funcs).ParseFS(templateFS,
+			"templates/layout.html",
+			"templates/_card.html",
+			"templates/"+p+".html",
+		)
+		if err != nil {
+			return nil, err
+		}
+		tpls[p] = t
+	}
+	s := &Server{cfg: cfg, tpls: tpls}
+	mux := http.NewServeMux()
+
+	staticSub, err := fs.Sub(staticFS, "static")
+	if err != nil {
+		return nil, err
+	}
+	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.FS(staticSub))))
+
+	mux.HandleFunc("GET /{$}", s.handleIndex)
+	for _, ch := range channels {
+		ch := ch
+		mux.HandleFunc("GET /"+ch.Slug, func(w http.ResponseWriter, r *http.Request) {
+			s.handleChannel(w, r, ch)
+		})
+	}
+	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+
+	s.srv = &http.Server{
+		Addr:              cfg.ListenAddr,
+		Handler:           mux,
+		ReadHeaderTimeout: 5 * time.Second,
+	}
+	return s, nil
+}
+
+// Start runs the HTTP server and blocks until ctx is canceled.
+func (s *Server) Start(ctx context.Context) {
+	go func() {
+		<-ctx.Done()
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		_ = s.srv.Shutdown(shutdownCtx)
+	}()
+	slog.Info("web server listening", "addr", s.cfg.ListenAddr)
+	if err := s.srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		slog.Error("web server crashed", "err", err)
+	}
+}