Compression across the board: directory answers, uploads, metrics, traces, the page (#253)

Measured 2026-10-16, uncompressed until now: the directory's answers (the feed list ipx reads,
603 KB of JSON, ~134 ms of a 159 ms Directory request), ipx's snapshot upload (~100 KB each half
hour), both /metrics (4.7 and 0.9 KB every 15 s) and every trace export to Tempo. Already
compressed: ipx-web's answers (zstd, #239), the home page and the directory's public pages
through Cloudflare (brotli, zstd).

- The directory compresses with brotli, zstd or gzip as asked, and unpacks a gzipped request.
- ipx sends its snapshot gzipped; the directory is deployed first.
- Both /metrics answer gzipped, as Prometheus asks.
- opentelemetry-otlp's gzip-http: OTEL_EXPORTER_OTLP_COMPRESSION=gzip compresses the export, set
  for all three in production's compose file; Caddy's exporter reads the same variable.
- web/build.mjs writes .br (quality 11) and .gz (level 9) beside each text file, and Caddy serves
  them in place (file_server precompressed): app.js 30 KB where zstd on the fly gave 37, app.css
  11 where 14. A .br or .gz asked for by name is refused, or /admin.js.br would be the admin
  page's script without the check that keeps it to admins; in a handle of its own, since a bare
  respond runs after the handles.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.lock

@@ -1868,6 +1868,7 @@ dependencies = [
  "axum",
  "chrono",
  "clap",
+ "flate2",
  "futures-util",
  "ipx-directory",
  "ipx-feed",
@@ -1901,6 +1902,7 @@ dependencies = [
  "anyhow",
  "axum",
  "clap",
+ "flate2",
  "futures-util",
  "ipx-feed",
  "mimalloc",
@@ -1916,6 +1918,7 @@ dependencies = [
  "tokio",
  "toml",
  "tower",
+ "tower-http 0.7.1",
  "tracing",
  "tracing-opentelemetry",
  "tracing-subscriber",
@@ -2850,6 +2853,7 @@ version = "0.33.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "699a67345e21962a231955b9059a157e428b219fa5df8efe11f08346fb23a344"
 dependencies = [
+ "flate2",
  "http",
  "httpdate",
  "opentelemetry",
@@ -4690,6 +4694,7 @@ version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08a05a66a4fdd61cbbe0a1d755ffe0ca6aba159dd4820936a0ff8a8278245b9c"
 dependencies = [
+ "async-compression",
  "bitflags 2.13.1",
  "bytes",
  "futures-core",