feat: 跨实例同步移植 WIP 检查点（第1轮+2a+2b+synced_servers）

从 Axolotl 移植跨实例同步子系统，当前进度：

- 第1轮：synced_options/files.rs + mod.rs 骨架，state 层补齐 SyncedOption/InstanceSyncedOptions/CanonicalValue/GameOptionKind 等

- 2a：game_options 的 api_types/options_file/catalog(10文件)

- 2b：game_options 除 resource_pack_options/local_settings_editor 外的全部（settings_editor/write_shared_settings/fullscreen/launch_overrides/instance_support/read_instance_changes/pack_updates/source_selection + locales/5文件）；State 补 synced_options_lock/game_locale_indexer/lock_synced_options

- synced_servers：6 文件全部搬入

- 35+20 处 sqlx::query! 宏改写为非宏 query+bind

已知未完成：synced_servers::operations 依赖 synced_options::instance_option_supported（属 orchestration，第5轮），当前编译不通。

packages/app-lib/src/api/instance/synced_options/pending.rs

@@ -0,0 +1,104 @@
+use super::files::synced_options_path;
+use crate::State;
+use crate::state::SyncedOption;
+use crate::util::io;
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum SyncedOptionJoinResolution {
+    UseSynced,
+    UseInstance,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "action", rename_all = "snake_case")]
+pub(super) enum PendingAction {
+    SelectSource,
+    Join {
+        resolution: Option<SyncedOptionJoinResolution>,
+    },
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub(super) struct PendingChange {
+    pub instance_id: String,
+    pub option: SyncedOption,
+    pub action: PendingAction,
+}
+
+pub(super) async fn read(state: &State) -> crate::Result<Vec<PendingChange>> {
+    let path = synced_options_path(state).join("pending-changes.json");
+    match tokio::fs::read(path).await {
+        Ok(bytes) => Ok(serde_json::from_slice(&bytes)?),
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
+            Ok(Vec::new())
+        }
+        Err(error) => Err(error.into()),
+    }
+}
+
+async fn write(changes: &[PendingChange], state: &State) -> crate::Result<()> {
+    let directory = synced_options_path(state);
+    io::create_dir_all(&directory).await?;
+    let temporary = directory.join("pending-changes.json.tmp");
+    io::write(&temporary, serde_json::to_vec(changes)?).await?;
+    tokio::fs::rename(temporary, directory.join("pending-changes.json"))
+        .await?;
+    Ok(())
+}
+
+/// Callers hold the synced-options lock while updating or replaying requests.
+pub(super) async fn save(
+    change: PendingChange,
+    state: &State,
+) -> crate::Result<()> {
+    let mut changes = read(state).await?;
+    changes.retain(|previous| {
+        previous.option != change.option
+            || (change.action != PendingAction::SelectSource
+                && previous.instance_id != change.instance_id)
+    });
+    changes.push(change);
+    write(&changes, state).await
+}
+
+pub(super) async fn remove(
+    change: &PendingChange,
+    state: &State,
+) -> crate::Result<()> {
+    let mut changes = read(state).await?;
+    let previous_len = changes.len();
+    changes.retain(|previous| previous != change);
+    if changes.len() != previous_len {
+        write(&changes, state).await?;
+    }
+    Ok(())
+}
+
+pub(super) async fn cancel(
+    option: SyncedOption,
+    instance_id: Option<&str>,
+    state: &State,
+) -> crate::Result<()> {
+    let mut changes = read(state).await?;
+    let previous_len = changes.len();
+    changes.retain(|change| {
+        change.option != option
+            || instance_id.is_some_and(|id| change.instance_id != id)
+    });
+    if changes.len() != previous_len {
+        write(&changes, state).await?;
+    }
+    Ok(())
+}
+
+pub(in crate::api::instance) async fn contains(
+    instance_id: &str,
+    option: SyncedOption,
+    state: &State,
+) -> crate::Result<bool> {
+    Ok(read(state).await?.iter().any(|change| {
+        change.instance_id == instance_id && change.option == option
+    }))
+}