all: remove HLS/VMAP support, use MP4-only video playback

Drops hls.js, the HLS glue JS, M3U8 manifest rewriting, VMAP resolution,
and the proxyVideos/hlsPlayback preferences. Videos now render as native
<video> elements with the highest-resolution MP4 variant. Promo card videos
that only provide HLS/VMAP streams show as unavailable since those are ads.

config/teapot.example.toml

@@ -50,7 +50,4 @@ replaceTwitter = ""
 replaceYouTube = ""
 replaceReddit = ""
 
-# Media handling
-proxyVideos = true
-hlsPlayback = false
 infiniteScroll = false