Add anime and foss channel themes

Two new web-only channels alongside EU: anime (🌸 sakura pink #ec5e8a)
and foss (🐧 amber #d97706). Both get the full bg/text/decoration/
border/glow theme classes.

internal/web/server.go

@@ -36,6 +36,8 @@ var channels = []Channel{
 	{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."},
+	{Slug: "anime", Title: "Anime", Theme: "anime", Emoji: "🌸", Blurb: "Series, studios, and the wider world of anime and manga."},
+	{Slug: "foss", Title: "FOSS", Theme: "foss", Emoji: "🐧", Blurb: "Kernel, distros, and the wider free and open source software world."},
 }
 
 // Server is the HTTP server for Pete's web UI.