Implement guild system with multi-guild, spells, and combat casting

- Guild data model: world/guilds/*.toml defines guilds with stat growth,
  resource type (mana/endurance), spell lists, level caps, and race
  restrictions. Spells are separate files in world/spells/*.toml.

- Player resources: mana and endurance pools added to PlayerStats with
  DB migration. Passive regen for mana/endurance when out of combat.

- Guild commands: guild list/info/join/leave with multi-guild support.
  spells/skills command shows available spells per guild level.

- Spell casting: cast command works in and out of combat. Offensive
  spells queue as CombatAction::Cast and resolve on tick. Heal/utility
  spells resolve immediately out of combat. Mana/endurance costs,
  cooldowns, and damage types all enforced.

- Chargen integration: classes reference a guild via TOML field. On
  character creation, player auto-joins the seeded guild at level 1.
  Class selection shows "→ joins <Guild>" hint.

- Look command: now accepts optional target argument to inspect NPCs
  (stats/attitude), objects, exits, players, or inventory items.

- 4 guilds (warriors/rogues/mages/clerics) and 16 spells created for
  the existing class archetypes.

Made-with: Cursor

world/spells/shadow_step.toml

@@ -0,0 +1,8 @@
+name = "Shadow Step"
+description = "Vanish into the shadows and reappear behind your foe, landing a devastating precision strike."
+spell_type = "offensive"
+damage = 30
+damage_type = "physical"
+cost_endurance = 25
+cooldown_ticks = 5
+min_guild_level = 8