Port Brave Sync server to Rust

Use SQLite for persistence and generate Rust protobuf bindings at build time.

Add Docker image support for containerized deployment.

Co-Authored-By: codex <[email protected]>

schema/protobuf/sync_pb/client_commands.proto

@@ -0,0 +1,57 @@
+// Copyright 2012 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Sync protocol for communication between sync client and server.
+
+// If you change or add any fields in this file, update proto_visitors.h and
+// potentially proto_enum_conversions.{h, cc}.
+
+syntax = "proto2";
+
+option go_package = "./sync_pb";
+
+option java_multiple_files = true;
+option java_package = "org.chromium.components.sync.protocol";
+
+option optimize_for = LITE_RUNTIME;
+
+package sync_pb;
+
+message CustomNudgeDelay {
+  optional int32 datatype_id = 1;  // Datatype id.
+  optional int32 delay_ms = 2;     // Delay in milliseconds.
+}
+
+message ClientCommand {
+  // Time to wait before sending any requests to the server.
+  optional int32 set_sync_poll_interval = 1;  // in seconds
+  // This has been deprecated since M75.
+  optional int32 set_sync_long_poll_interval = 2 [deprecated = true];
+
+  optional int32 max_commit_batch_size = 3;
+
+  // Number of seconds to delay before the throttled client should retry.
+  optional int32 throttle_delay_seconds = 5;
+
+  // This has been deprecated since M109.
+  optional int32 client_invalidation_hint_buffer_size = 6 [deprecated = true];
+
+  // Time to wait before issuing a retry GU.
+  optional int32 gu_retry_delay_seconds = 7;
+
+  // A dictionary of custom nudge delays.
+  repeated CustomNudgeDelay custom_nudge_delays = 8;
+
+  // Configuration for commit quota of extension-related data types.
+  // The maximum count of tokens (=initial at browser startup) and the
+  // interval for refilling one more token if not at maximum.
+  optional int32 extension_types_max_tokens = 9;
+  optional int32 extension_types_refill_interval_seconds = 10;
+
+  // Extended nudge delay for data types with depleted quota.
+  optional int32 extension_types_depleted_quota_nudge_delay_seconds = 11;
+
+  reserved 4;
+  reserved "sessions_commit_delay_seconds";
+}