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.

proto/qpc/v1/moderation.proto

@@ -0,0 +1,68 @@
+syntax = "proto3";
+package qpc.v1;
+
+// Moderation service: report, ban, unban, list reports, list banned.
+// Method IDs: 420-424.
+
+message ReportMessageRequest {
+  // Encrypted report payload (asymmetric, admin-key only).
+  bytes encrypted_report = 1;
+  // Conversation ID where the reported message lives.
+  bytes conversation_id = 2;
+}
+
+message ReportMessageResponse {
+  bool accepted = 1;
+}
+
+message BanUserRequest {
+  // Identity key of the user to ban (32 bytes).
+  bytes identity_key = 1;
+  // Human-readable reason for the ban.
+  string reason = 2;
+  // Ban duration in seconds (0 = permanent).
+  uint64 duration_secs = 3;
+}
+
+message BanUserResponse {
+  bool success = 1;
+}
+
+message UnbanUserRequest {
+  bytes identity_key = 1;
+}
+
+message UnbanUserResponse {
+  bool success = 1;
+}
+
+message ListReportsRequest {
+  uint32 limit = 1;
+  uint32 offset = 2;
+}
+
+message ReportEntry {
+  uint64 id = 1;
+  bytes encrypted_report = 2;
+  bytes conversation_id = 3;
+  bytes reporter_identity = 4;
+  uint64 timestamp = 5;
+}
+
+message ListReportsResponse {
+  repeated ReportEntry reports = 1;
+}
+
+message ListBannedRequest {}
+
+message BannedUserEntry {
+  bytes identity_key = 1;
+  string reason = 2;
+  uint64 banned_at = 3;
+  // 0 = permanent ban.
+  uint64 expires_at = 4;
+}
+
+message ListBannedResponse {
+  repeated BannedUserEntry users = 1;
+}