feat: Add gRPC API Layer - Phase 6 Integration

Added Protobuf definitions and gRPC services for all CQ layers:

Protobuf Files (4):
- configuration.proto: 2 Commands + 3 Queries (5 RPCs)
- clubmembership.proto: 3 Commands + 3 Queries (6 RPCs)
- networkmembership.proto: 3 Commands + 3 Queries (6 RPCs)
- commission.proto: 5 Commands + 4 Queries (9 RPCs)

gRPC Services (4):
- ConfigurationService: SetConfigurationValue, Deactivate, GetByKey, GetAll, GetHistory
- ClubMembershipService: Activate, Deactivate, AssignFeature, Get, GetAll, GetHistory
- NetworkMembershipService: Join, Move, Remove, GetPosition, GetTree, GetHistory
- CommissionService: Calculate+Process+Withdraw (5 commands), Get queries (4)

Features:
- HTTP transcoding enabled via google.api.http annotations
- Auto-registration via ConfigureGrpcEndpoints
- MetaData pagination support
- Request/Response DTOs for all endpoints
- Integration with MediatR CQRS handlers

Total: 4 proto files, 4 service classes, 26 RPC endpoints
Build: ✅ Successful (0 errors)

src/CMSMicroservice.Protobuf/Protos/configuration.proto

@@ -0,0 +1,133 @@
+syntax = "proto3";
+
+package configuration;
+
+import "public_messages.proto";
+import "google/protobuf/empty.proto";
+import "google/protobuf/wrappers.proto";
+import "google/protobuf/timestamp.proto";
+import "google/api/annotations.proto";
+
+option csharp_namespace = "CMSMicroservice.Protobuf.Protos.Configuration";
+
+service ConfigurationContract
+{
+    rpc CreateOrUpdateConfiguration(CreateOrUpdateConfigurationRequest) returns (google.protobuf.Empty){
+        option (google.api.http) = {
+            post: "/Configuration/CreateOrUpdate"
+            body: "*"
+        };
+    };
+    rpc DeactivateConfiguration(DeactivateConfigurationRequest) returns (google.protobuf.Empty){
+        option (google.api.http) = {
+            post: "/Configuration/Deactivate"
+            body: "*"
+        };
+    };
+    rpc GetConfigurationByKey(GetConfigurationByKeyRequest) returns (GetConfigurationByKeyResponse){
+        option (google.api.http) = {
+            get: "/Configuration/GetByKey"
+        };
+    };
+    rpc GetAllConfigurations(GetAllConfigurationsRequest) returns (GetAllConfigurationsResponse){
+        option (google.api.http) = {
+            get: "/Configuration/GetAll"
+        };
+    };
+    rpc GetConfigurationHistory(GetConfigurationHistoryRequest) returns (GetConfigurationHistoryResponse){
+        option (google.api.http) = {
+            get: "/Configuration/GetHistory"
+        };
+    };
+}
+
+// CreateOrUpdate Command
+message CreateOrUpdateConfigurationRequest
+{
+    string key = 1;
+    string value = 2;
+    google.protobuf.StringValue description = 3;
+    int32 scope = 4; // ConfigurationScope enum: System=0, Network=1, Club=2, Commission=3
+}
+
+// Deactivate Command
+message DeactivateConfigurationRequest
+{
+    string key = 1;
+    google.protobuf.StringValue reason = 2;
+}
+
+// GetByKey Query
+message GetConfigurationByKeyRequest
+{
+    string key = 1;
+}
+
+message GetConfigurationByKeyResponse
+{
+    int64 id = 1;
+    string key = 2;
+    string value = 3;
+    string description = 4;
+    int32 scope = 5;
+    bool is_active = 6;
+    google.protobuf.Timestamp created = 7;
+    google.protobuf.Timestamp last_modified = 8;
+}
+
+// GetAll Query
+message GetAllConfigurationsRequest
+{
+    google.protobuf.Int32Value scope = 1;
+    google.protobuf.BoolValue is_active = 2;
+    int32 page_index = 3;
+    int32 page_size = 4;
+}
+
+message GetAllConfigurationsResponse
+{
+    messages.MetaData meta_data = 1;
+    repeated ConfigurationModel models = 2;
+}
+
+message ConfigurationModel
+{
+    int64 id = 1;
+    string key = 2;
+    string value = 3;
+    string description = 4;
+    int32 scope = 5;
+    bool is_active = 6;
+    google.protobuf.Timestamp created = 7;
+}
+
+// GetHistory Query
+message GetConfigurationHistoryRequest
+{
+    google.protobuf.Int64Value configuration_id = 1;
+    google.protobuf.StringValue key = 2;
+    int32 page_index = 3;
+    int32 page_size = 4;
+}
+
+message GetConfigurationHistoryResponse
+{
+    messages.MetaData meta_data = 1;
+    repeated ConfigurationHistoryModel models = 2;
+}
+
+message ConfigurationHistoryModel
+{
+    int64 id = 1;
+    int64 configuration_id = 2;
+    string key = 3;
+    string old_value = 4;
+    string new_value = 5;
+    string old_description = 6;
+    string new_description = 7;
+    int32 old_scope = 8;
+    int32 new_scope = 9;
+    string performed_by = 10;
+    string reason = 11;
+    google.protobuf.Timestamp created = 12;
+}