Rate-limit CLI update notices

[clockwork-labs-bot]

Description of Changes

Fixes #5183.

This rate-limits the CLI update notice so the same advertised latest version is printed at most once every 24 hours. It keeps the existing 24 hour release lookup cache and adds backward-compatible notice metadata to the same cache file.

API and ABI breaking changes

None.

Expected complexity level and risk

1. The change is local to the lightweight update notice cache path and only affects how often the notice is printed.

Testing

• cargo fmt --all
• cargo test -p spacetimedb-update update_notice
• Manual binary check with cargo run:

tmpdir=$(mktemp -d)
mkdir -p "$tmpdir/config"
printf '{"last_check_secs":4102444800,"latest_version":"999.0.0"}' > "$tmpdir/config/.update_check_cache"

cargo build -p spacetimedb-cli -p spacetimedb-update
SPACETIMEDB_UPDATE_MULTICALL_APPLET=spacetime cargo run -p spacetimedb-update -- --root-dir="$tmpdir" help 2> /tmp/update-notice-1.err >/tmp/update-notice-1.out
SPACETIMEDB_UPDATE_MULTICALL_APPLET=spacetime cargo run -p spacetimedb-update -- --root-dir="$tmpdir" help 2> /tmp/update-notice-2.err >/tmp/update-notice-2.out

rg "A new version of SpacetimeDB is available" /tmp/update-notice-1.err
! rg "A new version of SpacetimeDB is available" /tmp/update-notice-2.err

[bfops]

Manual testing instruction incorrect:

   Compiling spacetimedb-update v2.3.0 (/home/work/SpacetimeDBPrivate/public/crates/update)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.48s
     Running `target/debug/spacetimedb-update --root-dir /tmp/tmp.SS56CGJ467 help`
Error: a value is required for '--root-dir <root_dir>' but none was supplied
```

[bfops]

LGTM. I ran the manual testing instructions