feat: initial meshservice implementation

Generic decentralized service layer for mesh networks.
Includes FAPP (psychotherapy) and Housing as reference services.

- ServiceMessage with Ed25519 signatures
- Wire protocol (64-byte header + CBOR)
- ServiceRouter with pluggable handlers
- Verification framework (3 trust levels)
- 32 tests, 3 examples

target/debug/.fingerprint/thiserror-impl-d2297da7a6dd2c94/lib-thiserror_impl.json

@@ -0,0 +1 @@
+{"rustc":1100337564441796057,"features":"[]","declared_features":"[]","target":6216210811039475267,"profile":2225463790103693989,"path":16008645068612253695,"deps":[[4289358735036141001,"proc_macro2",false,1225562667690107950],[10420560437213941093,"syn",false,15577739431691687943],[13111758008314797071,"quote",false,11911208238803379017]],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/thiserror-impl-d2297da7a6dd2c94/dep-lib-thiserror_impl","checksum":false}}],"rustflags":[],"config":2069994364910194474,"compile_kind":0}