Implement auth, persistence, typed responses, and injectable RNG

Auth: JWT tokens (sb-auth) with argon2 password hashing, login/register
endpoints, Bearer token middleware protecting all routes except auth.
Authorization checks ensure users can only access their own characters.

Persistence: SQLite via rusqlite (sb-db) with write-through on all
mutations. Optional via SB_DB_PATH env var; falls back to in-memory.

Typed responses: ~20 response DTOs in sb-shared replacing ad-hoc JSON.

Combat: Injectable RNG via &mut impl Rng for deterministic tests.

Clean Architecture: Combat types and response DTOs in sb-shared; domain
services in sb-core; auth in sb-auth; persistence in sb-db.

crates/sb-core/src/data.rs

@@ -0,0 +1,63 @@
+use serde::{Deserialize, Serialize};
+
+const ENEMIES_JSON: &str =
+    include_str!("../../../../skara-brae-common/data/enemies.json");
+const ZONES_JSON: &str =
+    include_str!("../../../../skara-brae-common/data/adventures/zones.json");
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EnemyDef {
+    pub id: String,
+    pub name: String,
+    pub level: i32,
+    pub stats: EnemyStats,
+    pub hp: i32,
+    pub attack_type: String,
+    pub damage: i32,
+    pub defense: i32,
+    pub xp: i32,
+    pub gold_min: i32,
+    pub gold_max: i32,
+    pub loot: Vec<LootDrop>,
+    pub description: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LootDrop {
+    pub item_id: String,
+    pub chance: f64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EnemyStats {
+    pub strength: i64,
+    pub intelligence: i64,
+    pub dexterity: i64,
+    pub constitution: i64,
+    pub luck: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EncounterEntry {
+    pub enemy_id: String,
+    pub weight: i32,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ZoneDef {
+    pub id: String,
+    pub name: String,
+    pub min_level: i32,
+    pub max_level: i32,
+    pub nerve_cost: i32,
+    pub description: String,
+    pub encounters: Vec<EncounterEntry>,
+}
+
+pub fn load_enemies() -> Vec<EnemyDef> {
+    serde_json::from_str(ENEMIES_JSON).expect("failed to parse enemies.json")
+}
+
+pub fn load_zones() -> Vec<ZoneDef> {
+    serde_json::from_str(ZONES_JSON).expect("failed to parse zones.json")
+}