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/cards.rs

@@ -1,5 +1,5 @@
 use axum::{
-    extract::{Query, State},
+    extract::{Path, Query, State},
     Json,
 };
 use serde::Deserialize;
@@ -7,7 +7,7 @@ use serde_json::{json, Value};
 
 use crate::{
     app::AppState,
-    error::AppResult,
+    error::{AppError, AppResult},
     models::card::OwnedCard,
     services::{club as club_svc, profile as profile_svc},
 };
@@ -18,6 +18,17 @@ pub struct CardQuery {
     pub position: Option<String>,
 }
 
+pub async fn get_card(
+    State(state): State<AppState>,
+    Path(card_id): Path<String>,
+) -> AppResult<Json<Value>> {
+    let card = state
+        .card_db
+        .get(&card_id)
+        .ok_or_else(|| AppError::NotFound(format!("card '{card_id}' not found")))?;
+    Ok(Json(json!({ "card": card })))
+}
+
 pub async fn get_cards(
     State(state): State<AppState>,
     Query(query): Query<CardQuery>,