feat: Phase 1 — core game loop complete

New endpoints:
- GET  /cards/:card_id       single card lookup
- POST /packs/buy            purchase pack with coins
- POST /objectives/claim     claim completed objective reward
- GET  /matches              match history (limit/mode query params)
- GET  /sbc/:sbc_id          single SBC lookup

Card pool expanded:
- Bronze: 11 → 30 cards (19 nations)
- Silver: 0 → 20 cards (20 nations)
- Rare Gold: 0 → 10 cards (10 nations)

SBC pool expanded:
- Added 5 new SBCs (tri_nations, silver_to_gold, league_loyalty,
  african_stars, gold_standard)

Infrastructure:
- SQLite WAL mode enabled on pool init
- Foreign key enforcement enabled

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

src/routes/sbc.rs

@@ -1,9 +1,12 @@
-use axum::{extract::State, Json};
+use axum::{
+    extract::{Path, State},
+    Json,
+};
 use serde_json::{json, Value};
 
 use crate::{
     app::AppState,
-    error::AppResult,
+    error::{AppError, AppResult},
     models::sbc::{SbcResult, SubmitSbcRequest},
     services::{club as club_svc, profile as profile_svc, sbc as sbc_svc},
 };
@@ -12,6 +15,18 @@ pub async fn get_sbcs(State(state): State<AppState>) -> AppResult<Json<Value>> {
     Ok(Json(json!({ "sbcs": state.sbc_defs })))
 }
 
+pub async fn get_sbc(
+    State(state): State<AppState>,
+    Path(sbc_id): Path<String>,
+) -> AppResult<Json<Value>> {
+    let sbc = state
+        .sbc_defs
+        .iter()
+        .find(|s| s.id == sbc_id)
+        .ok_or_else(|| AppError::NotFound(format!("SBC '{sbc_id}' not found")))?;
+    Ok(Json(json!({ "sbc": sbc })))
+}
+
 pub async fn post_sbc_submit(
     State(state): State<AppState>,
     Json(req): Json<SubmitSbcRequest>,