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.toml

@@ -15,13 +15,14 @@ anyhow = "1.0.104"
 argon2 = "0.6.0"
 atom_syndication = "0.12.10"
 axum = "0.8.9"
+flate2 = "1.1.10"
 chrono = { version = "0.4.45", default-features = false, features = ["std", "clock"] }
 clap = { version = "4.6.6", features = ["derive"] }
 futures-util = { version = "0.3.34", default-features = false, features = ["std"] }
 jsonwebtoken = { version = "11.1.0", default-features = false, features = ["aws_lc_rs"] }
 librqbit = { version = "9.0.1", default-features = false, features = ["rust-tls", "http-api-client"] }
 opentelemetry = { version = "0.33", default-features = false, features = ["trace"] }
-opentelemetry-otlp = { version = "0.33", default-features = false, features = ["trace", "http-proto", "reqwest-blocking-client"] }
+opentelemetry-otlp = { version = "0.33", default-features = false, features = ["trace", "http-proto", "reqwest-blocking-client", "gzip-http"] }
 opentelemetry_sdk = { version = "0.33", default-features = false, features = ["trace"] }
 opml = "1.1.6"
 mimalloc = "0.1.52"
@@ -36,7 +37,7 @@ sha2 = "0.10.9"
 tokio = { version = "1.53.1", features = ["rt-multi-thread", "macros", "fs", "io-util", "net", "sync", "time", "signal", "process"] }
 toml = "1.1.5"
 tower = { version = "0.5.3", features = ["util"] }
-tower-http = { version = "0.7.1", features = ["fs"] }
+tower-http = { version = "0.7.1", features = ["fs", "compression-br", "compression-gzip", "compression-zstd", "decompression-gzip"] }
 tracing = "0.1.44"
 tracing-opentelemetry = { version = "0.34", default-features = false }
 tracing-subscriber = { version = "0.3.23", features = ["env-filter", "json"] }