feat: FAPP — Free Appointment Propagation Protocol for psychotherapy discovery

docs/status.md

@@ -1,5 +1,32 @@
 # Status Log
 
+## 2026-03-31 — FAPP: Free Appointment Propagation Protocol
+
+### Completed
+- **Protocol spec** — `docs/specs/fapp-protocol.md`: decentralized psychotherapy appointment discovery over mesh
+- **Rust module** — `crates/quicprochat-p2p/src/fapp.rs`: full data structures, store, query matching, signature verification
+- **Message types**: SlotAnnounce, SlotQuery, SlotResponse, SlotReserve, SlotConfirm
+- **Domain model**: Fachrichtung, Modalitaet, Kostentraeger, SlotType (German enum names for domain concepts)
+- **FappStore**: in-memory cache with dedup (therapist_address + sequence), TTL expiry, signature verification, capacity limits
+- **Query matching**: filter by Fachrichtung, Modalitaet, Kostentraeger, PLZ prefix, time range, SlotType, max_results
+- **Tests**: 16 inline tests covering creation, signing, verification, tampering, forwarding, expiry, CBOR roundtrip, store dedup, sequence supersede, query filters (PLZ, SlotType, Kostentraeger, max_results)
+- **Privacy model**: therapist identity public (Approbation-bound), patient queries anonymous
+
+### Design Decisions
+- Extends announce.rs capability bitfield with CAP_FAPP_THERAPIST (0x0100), CAP_FAPP_RELAY (0x0200), CAP_FAPP_PATIENT (0x0400)
+- Uses same signing pattern as MeshAnnounce: hop_count excluded from signature, forwarding nodes don't re-sign
+- CBOR wire format consistent with existing envelope/announce code
+- Location hint is PLZ only (e.g. "80331") — never exact address
+- Anti-spam: Approbation hash binding, signature verification, sequence-based dedup, rate limiting, TTL enforcement
+
+### What's Next
+- Integrate FAPP message handling into mesh_router.rs
+- SlotReserve/SlotConfirm E2E encryption (X25519 key exchange)
+- Return-path routing for anonymous SlotQuery responses
+- Rate limiting per therapist address in FappStore
+
+---
+
 ## 2026-03-30 — Implementation Sprint (S4-S5 + MLS-Lite)
 
 ### Completed