feat: cross-enclave sync via kt-<host>:<port> network (#1378)

## Summary

- Lets one Kurtosis enclave sync from another. Source enclave A runs
`apache` and publishes the canonical bal-devnet metadata files
(`/enodes.txt`, `/bootstrap_nodes.txt`, `/bootstrap_nodes.yaml`,
`/network-config.tar`) at the URL root.
- Target enclave B sets `network: kt-<A-host>:<A-apache-port>`, fetches
the tar, and bootstraps off A's enodes/ENRs via the existing devnet code
paths in the EL/CL launchers — no client launcher changes needed.
- Validator counts auto-zero on the target (existing logic for
non-`kurtosis`/`shadowfork` networks), so target is observer-mode by
default.

## Changes

- `src/apache/apache_launcher.star`, `src/nginx/nginx_launcher.star`
- Rename file constants to canonical bal-devnet names (`boot_enr.yaml` →
`bootstrap_nodes.yaml`, `bootnode.txt` → `enodes.txt`;
`bootstrap_nodes.txt` already matched).
- Fix `cp -R /network-configs /htdocs/` → `cp -R /network-configs/.
/htdocs/` so files land at the URL root, not nested under
`/network-configs/`.
- `src/apache/apache_launcher.star`
- Print the exact `kt-<host>:<port>` string the operator should use on a
sync target.
- Warn when `port_publisher.el.nat_exit_ip` is unset (otherwise
published enodes advertise unreachable docker IPs).
- `src/network_launcher/remote_enclave.star` (new)
- Parses `kt-<host>:<port>` (also accepts `kt-http://...` /
`kt-https://...`).
- Curls `<base>/network-config.tar`, extracts to the
`el_cl_genesis_data` artifact, reads timestamp + network_id from the
embedded `config.yaml`.
- `src/package_io/constants.star`
  - Adds `NETWORK_NAME.remote_enclave = "kt-"` (used as a prefix).
- `src/participant_network.star`
- New `elif network_params.network.startswith("kt-")` branch dispatches
to the new launcher, placed before the public/devnet fallbacks.

## Breaking change

The apache/nginx services no longer serve files under the legacy names
`boot_enr.yaml` and `bootnode.txt`. Anyone scraping those URLs needs to
switch to `bootstrap_nodes.yaml` and `enodes.txt`.

## Caveat

Geth's snap-sync wedges with `missing trie node ... layer stale` when
joining a fresh kurtosis devnet mid-flight. Not specific to
cross-enclave sync — same issue affects any kurtosis-to-snapshot path.
Mitigations:
- Use `el_extra_params: [--syncmode=full]` on the target (proven to work
in testing), or
- Wait until the source enclave has finalized at least one epoch before
launching the target.

## Test plan

- [x] Local 2-enclave test on one host (10.100.116.15)
- A: 2 nodes (geth+lighthouse, reth+teku) + apache on port 9128,
`port_publisher.{el,cl}.enabled: true`, `nat_exit_ip: 10.100.116.15`.
- B: 1 node (geth+lighthouse) with `network: kt-10.100.116.15:9128` and
`--syncmode=full`.
- Result: A EL block `0x38` == B EL block `0x38`, B CL `sync_distance:
0`, B's geth importing chain segments. EL+CL peering established
cross-enclave (2 EL peers, 2 CL peers).
- [x] Verified canonical files served at root and that enodes advertise
the public NAT IP, not docker-internal:
  - `/enodes.txt` contains `enode://...@10.100.116.15:32000`
- `/bootstrap_nodes.txt`, `/bootstrap_nodes.yaml`, `/network-config.tar`
all 200 OK
- [ ] Remote-machine test (two physical hosts) — pending.

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Signed-off-by: Barnabas Busa <barnabas.busa@ethereum.org>

Author: barnabasbusa