Cardano Updates

Add --max-retries (default: 7) and --max-concurrent-downloads
(default: 10) flags to `foliage build`.

With 7 retries, curl's exponential backoff spans 1+2+4+8+16+32+64 =
127 seconds, giving GitHub ample time to recover from transient 502s.

Lowering concurrent downloads from 20 to 10 further reduces server
pressure under high parallelism (-j 0).

Updates the foliage flake input to include input-output-hk/foliage#116:

- curl --retry 3 --retry-connrefused for transient HTTP errors (502, etc.)
  with exponential backoff
- Download concurrency capped at 20 via Shake Resource to prevent
  overwhelming GitHub under -j 0
- CI actions upgraded (nix-installer v21, magic-nix-cache v13, cachix v16)

- DeterminateSystems/nix-installer-action: v9 → v21
- DeterminateSystems/magic-nix-cache-action: v2 → v13
- cachix/cachix-action: v14 → v16

Fixes CI failures caused by TypeError: Invalid URL in the old
nix-installer-action when fetching from install.determinate.systems.

Fix transient HTTP 502 failures when downloading source tarballs from
GitHub under high parallelism (-j 0).

Two changes:

1. Add --retry 3 --retry-connrefused to curl invocations. Curl retries
   transient HTTP errors (408, 429, 500, 502, 503, 504) with built-in
   exponential backoff (1s, 2s, 4s). The existing actionRetry 5 is kept
   as a second layer for non-HTTP failures.

2. Cap concurrent downloads at 20 using Shake's Resource mechanism.
   This prevents hundreds of simultaneous curl processes from
   overwhelming GitHub when running with -j 0. Non-network tasks
   (patching, sdist creation, index building) still run at full
   parallelism.

"Enforce max reconnection attempt" (f9ae41a8962174e4f7d7e93d81f70f1c88cef263)

"Removed ChurnCounter" (e23919769257b3dbfec5c62d47d2277ccbf1f792)

"Add behind firewall conf to prevent node from initiating connection to behind-firewall remote peer" (09f84dd286af402b5737d553dec0c19fbaa98e3a)

Includes network-mux instances in Network.Mux.Logging

Signed-off-by: Chris Gianelloni <[email protected]>