refactor: 拆分 gateway 单体为独立 crate，新增 systemd 部署方案

将 gateway 内部的 model-fetch、provider-transport、scheduler-core、
usage-runtime、video-tasks-core 模块提取为独立 crate；重构 gateway
内部模块结构（state/router/cache/data/query 等）；移除大量遗留模块
文件；新增 systemd 二进制部署骨架及相关文档；更新前端 usage 相关
API 和组件。

crates/aether-video-tasks-core/src/store_registry.rs

@@ -0,0 +1,100 @@
+use std::collections::BTreeMap;
+
+use serde::{Deserialize, Serialize};
+use serde_json::{Map, Value};
+
+use crate::{
+    GeminiVideoTaskSeed, LocalVideoTaskReadResponse, LocalVideoTaskRegistryMutation,
+    LocalVideoTaskSnapshot, LocalVideoTaskStatus, OpenAiVideoTaskSeed,
+};
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct VideoTaskRegistry {
+    openai: BTreeMap<String, LocalVideoTaskSnapshot>,
+    gemini: BTreeMap<String, LocalVideoTaskSnapshot>,
+}
+
+impl VideoTaskRegistry {
+    pub fn insert(&mut self, snapshot: LocalVideoTaskSnapshot) {
+        match &snapshot {
+            LocalVideoTaskSnapshot::OpenAi(seed) => {
+                self.openai.insert(seed.local_task_id.clone(), snapshot);
+            }
+            LocalVideoTaskSnapshot::Gemini(seed) => {
+                self.gemini.insert(seed.local_short_id.clone(), snapshot);
+            }
+        }
+    }
+
+    pub fn read_openai(&self, task_id: &str) -> Option<LocalVideoTaskReadResponse> {
+        self.openai
+            .get(task_id)
+            .map(LocalVideoTaskSnapshot::read_response)
+    }
+
+    pub fn read_gemini(&self, short_id: &str) -> Option<LocalVideoTaskReadResponse> {
+        self.gemini
+            .get(short_id)
+            .map(LocalVideoTaskSnapshot::read_response)
+    }
+
+    pub fn clone_openai(&self, task_id: &str) -> Option<OpenAiVideoTaskSeed> {
+        let LocalVideoTaskSnapshot::OpenAi(seed) = self.openai.get(task_id)?.clone() else {
+            return None;
+        };
+        Some(seed)
+    }
+
+    pub fn clone_gemini(&self, short_id: &str) -> Option<GeminiVideoTaskSeed> {
+        let LocalVideoTaskSnapshot::Gemini(seed) = self.gemini.get(short_id)?.clone() else {
+            return None;
+        };
+        Some(seed)
+    }
+
+    pub fn list_active_snapshots(&self, limit: usize) -> Vec<LocalVideoTaskSnapshot> {
+        self.openai
+            .values()
+            .chain(self.gemini.values())
+            .filter(|snapshot| snapshot.is_active_for_refresh())
+            .take(limit)
+            .cloned()
+            .collect()
+    }
+
+    pub fn apply_mutation(&mut self, mutation: LocalVideoTaskRegistryMutation) {
+        match mutation {
+            LocalVideoTaskRegistryMutation::OpenAiCancelled { task_id } => {
+                if let Some(LocalVideoTaskSnapshot::OpenAi(seed)) = self.openai.get_mut(&task_id) {
+                    seed.status = LocalVideoTaskStatus::Cancelled;
+                }
+            }
+            LocalVideoTaskRegistryMutation::OpenAiDeleted { task_id } => {
+                if let Some(LocalVideoTaskSnapshot::OpenAi(seed)) = self.openai.get_mut(&task_id) {
+                    seed.status = LocalVideoTaskStatus::Deleted;
+                }
+            }
+            LocalVideoTaskRegistryMutation::GeminiCancelled { short_id } => {
+                if let Some(LocalVideoTaskSnapshot::Gemini(seed)) = self.gemini.get_mut(&short_id) {
+                    seed.status = LocalVideoTaskStatus::Cancelled;
+                }
+            }
+        }
+    }
+
+    pub fn project_openai(&mut self, task_id: &str, provider_body: &Map<String, Value>) -> bool {
+        let Some(LocalVideoTaskSnapshot::OpenAi(seed)) = self.openai.get_mut(task_id) else {
+            return false;
+        };
+        seed.apply_provider_body(provider_body);
+        true
+    }
+
+    pub fn project_gemini(&mut self, short_id: &str, provider_body: &Map<String, Value>) -> bool {
+        let Some(LocalVideoTaskSnapshot::Gemini(seed)) = self.gemini.get_mut(short_id) else {
+            return false;
+        };
+        seed.apply_provider_body(provider_body);
+        true
+    }
+}