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/examples/multi_service.rs

@@ -0,0 +1,89 @@
+//! Multi-Service Demo
+//!
+//! Shows how multiple services can run on the same mesh router.
+
+use meshservice::{
+    capabilities,
+    identity::ServiceIdentity,
+    router::ServiceRouter,
+    service_ids,
+    services::{
+        fapp::{create_announce as fapp_announce, FappService, Modality, SlotAnnounce, Specialism},
+        housing::{
+            amenities, create_announce as housing_announce, HousingService, ListingAnnounce,
+            ListingType,
+        },
+    },
+    verification::{TrustedVerifiers, Verification, VerificationLevel},
+};
+
+fn main() {
+    println!("=== Multi-Service Mesh Demo ===\n");
+
+    // Create a router that handles both FAPP and Housing
+    let mut router = ServiceRouter::new(capabilities::RELAY | capabilities::CONSUMER);
+    router.register(Box::new(FappService::relay()));
+    router.register(Box::new(HousingService::relay()));
+
+    println!("Registered services:");
+    for (id, name) in router.services() {
+        println!("  0x{:04x} - {}", id, name);
+    }
+    println!();
+
+    // Create identities
+    let therapist = ServiceIdentity::generate();
+    let landlord = ServiceIdentity::generate();
+    let registry = ServiceIdentity::generate();
+
+    // Setup trusted verifiers
+    let mut verifiers = TrustedVerifiers::new();
+    verifiers.add(
+        registry.public_key(),
+        "Health Registry",
+        VerificationLevel::RegistryVerified,
+    );
+    router.set_trusted_verifiers(verifiers);
+
+    // Therapist announcement with verification
+    println!("--- Adding FAPP announcement ---");
+    let fapp_data = SlotAnnounce::new(&[Specialism::Psychoanalysis], Modality::InPerson, "104")
+        .with_profile("https://kbv.de/therapists/12345");
+
+    let mut fapp_msg = fapp_announce(&therapist, &fapp_data, 1).unwrap();
+
+    // Registry verifies therapist
+    let verification = Verification::registry(
+        &registry,
+        &therapist.address(),
+        "licensed_therapist",
+        "KBV-12345",
+    );
+    fapp_msg.add_verification(verification);
+
+    router.handle(fapp_msg, Some(therapist.public_key())).unwrap();
+    println!("FAPP announcement stored (with registry verification)\n");
+
+    // Housing announcement
+    println!("--- Adding Housing announcement ---");
+    let housing_data = ListingAnnounce::new(ListingType::Studio, 35, 700, "104")
+        .with_amenities(amenities::FURNISHED | amenities::INTERNET)
+        .with_title("Cozy studio near therapist offices");
+
+    let housing_msg = housing_announce(&landlord, &housing_data, 1).unwrap();
+    router.handle(housing_msg, Some(landlord.public_key())).unwrap();
+    println!("Housing announcement stored\n");
+
+    // Summary
+    println!("--- Store Summary ---");
+    println!("FAPP messages:    {}", router.store().service_count(service_ids::FAPP));
+    println!("Housing messages: {}", router.store().service_count(service_ids::HOUSING));
+    println!("Total messages:   {}", router.store().len());
+
+    println!("\n=== Multi-Service Demo Complete ===");
+    println!("\nThe mesh can route and store messages for multiple services");
+    println!("using a single router instance. Each service has its own:");
+    println!("  - Payload format");
+    println!("  - Query matching logic");
+    println!("  - Handler implementation");
+}