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/group.proto

@@ -0,0 +1,61 @@
+syntax = "proto3";
+package qpc.v1;
+
+// Group management (4 methods).
+// Method IDs: 410-413.
+
+// RemoveMember (410): Remove a member from a group.
+message RemoveMemberRequest {
+  bytes group_id = 1;
+  bytes member_identity_key = 2;
+}
+
+message RemoveMemberResponse {
+  bytes commit = 1;
+}
+
+// UpdateGroupMetadata (411): Set group name, description, avatar.
+message UpdateGroupMetadataRequest {
+  bytes group_id = 1;
+  string name = 2;
+  string description = 3;
+  bytes avatar_hash = 4;
+}
+
+message UpdateGroupMetadataResponse {
+  bool success = 1;
+}
+
+// ListGroupMembers (412): List members of a group.
+message ListGroupMembersRequest {
+  bytes group_id = 1;
+}
+
+message ListGroupMembersResponse {
+  repeated GroupMemberInfo members = 1;
+}
+
+message GroupMemberInfo {
+  bytes identity_key = 1;
+  string username = 2;
+  uint64 joined_at = 3;
+}
+
+// RotateKeys (413): Trigger key rotation (Update proposal + Commit).
+message RotateKeysRequest {
+  bytes group_id = 1;
+}
+
+message RotateKeysResponse {
+  bytes commit = 1;
+}
+
+// GroupMetadata stored server-side.
+message GroupMetadata {
+  bytes group_id = 1;
+  string name = 2;
+  string description = 3;
+  bytes avatar_hash = 4;
+  bytes creator_key = 5;
+  uint64 created_at = 6;
+}