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/QuicProChat/QpqError.swift

@@ -0,0 +1,23 @@
+/// Errors returned by the QuicProChat SDK.
+public enum QpqError: Error, Sendable, CustomStringConvertible {
+    /// Connection to the server failed.
+    case connectionFailed(String)
+    /// OPAQUE authentication failed (bad credentials).
+    case authFailed(String)
+    /// The operation timed out.
+    case timeout(String)
+    /// The client is not connected.
+    case notConnected
+    /// A generic error from the FFI layer.
+    case ffiError(String)
+
+    public var description: String {
+        switch self {
+        case .connectionFailed(let msg): return "connection failed: \(msg)"
+        case .authFailed(let msg): return "auth failed: \(msg)"
+        case .timeout(let msg): return "timeout: \(msg)"
+        case .notConnected: return "not connected"
+        case .ffiError(let msg): return "FFI error: \(msg)"
+        }
+    }
+}