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/models/objective.rs

@@ -55,3 +55,11 @@ pub struct ObjectiveWithProgress {
     pub completed: bool,
     pub claimed: bool,
 }
+
+#[derive(Debug, Serialize)]
+pub struct ClaimRewardResult {
+    pub objective_id: String,
+    pub coins_granted: i64,
+    pub xp_granted: i64,
+    pub pack_granted: Option<String>,
+}