chore: rename quicproquo → quicprochat in Rust workspace

Rename all crate directories, package names, binary names, proto
package/module paths, ALPN strings, env var prefixes, config filenames,
mDNS service names, and plugin ABI symbols from quicproquo/qpq to
quicprochat/qpc.

crates/quicprochat-plugin-api/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name        = "quicprochat-plugin-api"
+version     = "0.1.0"
+edition.workspace     = true
+description = "C-ABI vtable for quicprochat server plugins. No std dependency; usable from bare-metal plugin authors."
+license     = "Apache-2.0 OR MIT"
+repository.workspace  = true
+
+[lints]
+workspace = true
+
+# No dependencies — intentionally minimal so plugin authors have zero forced transitive deps.
+[dependencies]