feat: v2 Phase 1 — foundation, proto schemas, RPC framework, SDK skeleton

New workspace structure with 9 crates. Adds:

- proto/qpq/v1/*.proto: 11 protobuf schemas covering all 33 RPC methods
- quicproquo-proto: dual codegen (capnp legacy + prost v2)
- quicproquo-rpc: QUIC RPC framework (framing, server, client, middleware)
- quicproquo-sdk: client SDK (QpqClient, events, conversation store)
- quicproquo-server/domain/: protocol-agnostic domain types and services
- justfile: build commands

Wire format: [method_id:u16][req_id:u32][len:u32][protobuf] per QUIC stream.
All 151 existing tests pass. Backward compatible with v1 capnp code.

crates/quicproquo-rpc/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "quicproquo-rpc"
+version = "0.1.0"
+edition = "2021"
+description = "QUIC RPC framework for quicproquo v2 — framing, dispatch, tower middleware"
+
+[dependencies]
+quicproquo-proto = { path = "../quicproquo-proto" }
+prost            = { workspace = true }
+bytes            = { workspace = true }
+quinn            = { workspace = true }
+rustls           = { workspace = true }
+rcgen            = { workspace = true }
+tokio            = { workspace = true }
+futures          = { workspace = true }
+tower            = { workspace = true }
+tracing          = { workspace = true }
+thiserror        = { workspace = true }
+dashmap          = { workspace = true }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["test-util"] }
+
+[lints]
+workspace = true