feat(v2): implement ship host init with JSON output

- host_v2.go: full host initialization with JSON responses
- Installs Caddy, Docker on Ubuntu/Debian
- Creates /etc/ship/{env,ports,ttl} directories
- Installs TTL cleanup timer (hourly systemd timer)
- Cleanup script removes expired deploys completely
- Preserves git deploy setup functionality (optional)
- Added ErrInvalidArgs error code

Critical 'host init' functionality preserved for v2

1 files changed, 7 insertions, 2 deletions

diff --git a/PROGRESS.md b/PROGRESS.md
index c91fc1b..5096cf2 100644
--- a/PROGRESS.md
+++ b/PROGRESS.md
@@ -21,10 +21,15 @@ Tracking rebuilding ship for agent-first JSON interface.
 - [x] Port allocation (server-side)
 
 ## Upcoming
-- [ ] TTL cleanup timer (server-side cron)
-- [ ] `ship host init` (update to match spec)
 - [ ] `ship list/status/logs/remove` implementations
 - [ ] Wire up v2 commands in main.go (feature flag or replace)
+- [ ] Testing with real deploys
+
+## Completed Recently
+- [x] TTL cleanup timer (server-side systemd timer)
+- [x] `ship host init` with JSON output
+- [x] Docker + Caddy installation
+- [x] Cleanup script for expired TTL deploys
 
 ## Commits
 - `5b88935` feat(v2): add output and detect packages