chore: rename quicproquo → quicprochat in docs, Docker, CI, and packaging

Rename all project references from quicproquo/qpq to quicprochat/qpc
across documentation, Docker configuration, CI workflows, packaging
scripts, operational configs, and build tooling.

- Docker: crate paths, binary names, user/group, data dirs, env vars
- CI: workflow crate references, binary names, artifact names
- Docs: all markdown files under docs/, SDK READMEs, book.toml
- Packaging: OpenWrt Makefile, init script, UCI config (file renames)
- Scripts: justfile, dev-shell, screenshot, cross-compile, ai_team
- Operations: Prometheus config, alert rules, Grafana dashboard
- Config: .env.example (QPQ_* → QPC_*), CODEOWNERS paths
- Top-level: README, CONTRIBUTING, ROADMAP, CLAUDE.md

sdks/swift/Sources/CQuicProChat/quicprochat_ffi.h

@@ -0,0 +1,52 @@
+// quicprochat_ffi.h — C header for libquicprochat_ffi.
+//
+// Mirrors the extern "C" functions from crates/quicprochat-ffi/src/lib.rs.
+
+#ifndef QUICPROCHAT_FFI_H
+#define QUICPROCHAT_FFI_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Status codes.
+#define QPQ_OK             0
+#define QPQ_ERROR          1
+#define QPQ_AUTH_FAILED    2
+#define QPQ_TIMEOUT        3
+#define QPQ_NOT_CONNECTED  4
+
+// Opaque handle type.
+typedef struct QpqHandle QpqHandle;
+
+// Connect to a quicprochat server.  Returns NULL on failure.
+QpqHandle* qpq_connect(const char* server, const char* ca_cert, const char* server_name);
+
+// Authenticate with OPAQUE credentials.
+int qpq_login(QpqHandle* handle, const char* username, const char* password);
+
+// Send a message to a recipient (by username).
+int qpq_send(QpqHandle* handle, const char* recipient,
+             const uint8_t* message, size_t message_len);
+
+// Receive pending messages (blocking).  On success, *out_json is a
+// heap-allocated JSON string that must be freed with qpq_free_string.
+int qpq_receive(QpqHandle* handle, uint32_t timeout_ms, char** out_json);
+
+// Disconnect and free the handle.
+void qpq_disconnect(QpqHandle* handle);
+
+// Return the last error message, or NULL.  Do NOT free the result.
+const char* qpq_last_error(const QpqHandle* handle);
+
+// Free a string returned by qpq_receive.
+void qpq_free_string(char* ptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // QUICPROCHAT_FFI_H