feat(p2p): add MeshNode integrating all production modules

New mesh_node.rs providing a production-ready node:
- MeshNodeBuilder for fluent configuration
- MeshConfig integration for all settings
- MeshMetrics tracking for all operations
- Rate limiting on incoming messages
- Backpressure controller
- Graceful shutdown via ShutdownCoordinator
- Optional FappRouter based on capabilities
- MeshRouter for envelope routing
- TransportManager for multi-transport support

Key APIs:
- MeshNodeBuilder::new().fapp_relay().build()
- node.process_incoming() with rate limiting + metrics
- node.gc() for store/routing table cleanup
- node.shutdown() for graceful termination

222 tests passing (203 lib + 3 fapp_flow + 16 multi_node)

crates/meshservice/Cargo.toml

@@ -0,0 +1,43 @@
+[package]
+name = "meshservice"
+version = "0.1.0"
+edition = "2021"
+authors = ["Chris <c@xorwell.de>"]
+description = "Generic decentralized service layer for mesh networks"
+license = "MIT"
+repository = "https://git.xorwell.de/c/meshservice"
+keywords = ["mesh", "p2p", "decentralized", "services"]
+categories = ["network-programming"]
+
+[dependencies]
+# Serialization
+serde = { version = "1.0", features = ["derive"] }
+ciborium = "0.2"
+
+# Crypto
+ed25519-dalek = { version = "2.1", features = ["serde"] }
+sha2 = "0.10"
+rand = "0.8"
+x25519-dalek = "2.0"
+
+# Async
+tokio = { version = "1.36", features = ["sync", "time"] }
+
+# Error handling
+anyhow = "1.0"
+thiserror = "1.0"
+
+[dev-dependencies]
+tokio = { version = "1.36", features = ["rt-multi-thread", "macros"] }
+
+[[example]]
+name = "fapp_service"
+path = "examples/fapp_service.rs"
+
+[[example]]
+name = "housing_service"
+path = "examples/housing_service.rs"
+
+[[example]]
+name = "multi_service"
+path = "examples/multi_service.rs"