scaffold: Backend API routes, DB queries, and middleware stubs

88 handler stubs across 13 route files, 66 DB query stubs across
11 modules, auth/license extractors, and rate limit middleware.
All bodies are todo!() — ready for Phase 1b implementation.

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

backend/src/db/mod.rs

@@ -0,0 +1,14 @@
+// Database query modules — each corresponds to a domain
+// Queries use sqlx with compile-time verification against PostgreSQL
+
+pub mod users;
+pub mod licenses;
+pub mod servers;
+pub mod wipes;
+pub mod maps;
+pub mod plugins;
+pub mod teams;
+pub mod notifications;
+pub mod chat;
+pub mod stats;
+pub mod store;