fix(env_sync): use config port_bases instead of .env extraction to prevent compounding

sync_env_files was reading base ports from .env files, which caused ports
to compound by +20 on every restart (e.g., 3220 → 3381 over 9 restarts).

Now reads base ports from env_sync.port_bases in config — the same source
of truth used by show_ports and get_workspace_ports.

Also adds admin-app port management (PORT, API_PORT) which was previously
unmanaged, causing cross-workspace collisions.

Changes:
- Add port_bases config format (map of type → base port)
- Add get_port_base() and get_port_types() helpers
- Rewrite read_env_port() to handle new map format + old array backward compat
- Rewrite sync_env_files first pass to use config bases
- Dynamic show_ports columns from port types
- Update template_promptfoo_cloud with new format
- Handle missing .env files and vars (create/append)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MrFlounder