Initial commit: OpenFUT Core

Offline Ultimate Team backend — game-independent REST API.

- 19 API endpoints: auth, profiles, clubs, cards, packs, squads,
  objectives, SBCs, match rewards, NPC market, statistics
- Axum + SQLite + SQLx with full migrations
- Weighted pack generator, SBC validation engine
- JSON-driven mod data (cards, packs, objectives, SBCs)
- 5 integration tests passing

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

src/modding/mod.rs

@@ -0,0 +1,4 @@
+//! Modding support: load JSON data files from the data/ directory.
+//! All game content (cards, packs, objectives, SBCs) is data-driven.
+
+pub mod loader;