Implements the new player funnel with two tutorial zones:
- Flower: 7x7 sealed zone with translucent petals, spawn at center
- Treehouse: 20x15 platform zone with rope ladder and branch exits
Both zones are bounded (non-toroidal) and include portals for progression.
Implements load_zone() and load_zones() functions to parse zone
definitions from TOML files. Wires zone loading into server startup
to register all zones from content/zones/ directory. Updates player
zone lookup to use the registry instead of hardcoded overworld check.
Includes tavern.toml as first hand-built interior zone (8x6 bounded).
