Add full-text search, EU channel theme, and web-only sources

Search: new FTS5-backed SearchStories query, /search JSON endpoint,
client-side overlay (search.js) wired into the layout header. EU
channel gets its own theme color (#003399) across bg/text/border/glow
classes. Sources can now route to non-Matrix channels without
validation error (web-only mode); a warning still flags typos.

internal/web/server.go

@@ -34,6 +34,7 @@ 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."},
+	{Slug: "eu", Title: "EU", Theme: "eu", Emoji: "🇪🇺", Blurb: "Portugal and the wider European beat. Read-only — these stories don't post to Matrix."},
 	{Slug: "music", Title: "Music", Theme: "music", Emoji: "🎵", Blurb: "Records, scenes, and the artists shaping the sound."},
 }
 
@@ -73,6 +74,7 @@ func New(cfg config.WebConfig) (*Server, error) {
 
 	mux.HandleFunc("GET /{$}", s.handleIndex)
 	mux.HandleFunc("GET /weather", s.handleWeatherDemo)
+	mux.HandleFunc("GET /api/search", s.handleSearch)
 	for _, ch := range channels {
 		ch := ch
 		mux.HandleFunc("GET /"+ch.Slug, func(w http.ResponseWriter, r *http.Request) {