Promote service modules to services/ directory; add AmqpConnection + async IPL

- Flat src/amqp.rs, src/mongo.rs, src/mariadb.rs promoted to src/services/{amqp,mongo,mariadb}/
- services/amqp/connection.rs: AmqpConnection struct with connect() and declare_exchange()
- services/amqp/error.rs: AmqpError type (thiserror, wraps lapin::Error)
- ipl() made async; #[tokio::main] added to main()
- IPL step 3b: authenticate to RabbitMQ + declare beds.events topic exchange (durable)
- Added lapin = "2" and tokio = { version = "1", features = ["full"] } to Cargo.toml
- 12 unit tests pass
- Docs: README, CLAUDE.md, wiki/04-ipl.md, wiki/06-queue-topology.md updated

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

src/lib.rs

@@ -12,9 +12,8 @@
 //!
 //! ## History
 //! * `2026-04-02` - mks - original coding
+//! * `2026-04-04` - mks - promoted service modules to pub mod services
 
-pub mod amqp;
 pub mod config;
 pub mod logging;
-pub mod mariadb;
-pub mod mongo;
+pub mod services;