feat: async insight generation with SQLite job tracking

- Add insight_generation_jobs table migration and DAO
- Implement job lifecycle: create_or_get_active, complete, fail, cancel
- Refactor POST /insights/generate and /agentic to async spawn with timeout
- Add GET /insights/generation/status endpoint with job_id and file_path lookup
- Use String for enum fields in Diesel models to avoid private Bound type
- Add from_str() helpers on InsightJobStatus and InsightGenerationType
- Fix update_training_messages to return Result<usize, DbError>
- 7/7 DAO unit tests passing

src/database/models.rs

@@ -1,9 +1,81 @@
 use crate::database::schema::{
-    entities, entity_facts, entity_photo_links, favorites, image_exif, libraries, personas,
-    photo_insights, users, video_preview_clips,
+    entities, entity_facts, entity_photo_links, favorites, image_exif, insight_generation_jobs,
+    libraries, personas, photo_insights, users, video_preview_clips,
 };
 use serde::Serialize;
 
+/// Possible statuses for an insight generation job.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, FromSqlRow)]
+#[serde(rename_all = "snake_case")]
+pub enum InsightJobStatus {
+    Running,
+    Completed,
+    Failed,
+    Cancelled,
+}
+
+impl InsightJobStatus {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::Running => "running",
+            Self::Completed => "completed",
+            Self::Failed => "failed",
+            Self::Cancelled => "cancelled",
+        }
+    }
+}
+
+impl ToString for InsightJobStatus {
+    fn to_string(&self) -> String {
+        self.as_str().to_string()
+    }
+}
+
+impl InsightJobStatus {
+    pub fn from_str(s: &str) -> Self {
+        match s {
+            "running" => Self::Running,
+            "completed" => Self::Completed,
+            "failed" => Self::Failed,
+            "cancelled" => Self::Cancelled,
+            _ => Self::Failed,
+        }
+    }
+}
+
+/// Type of insight generation (standard vs agentic).
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum InsightGenerationType {
+    Standard,
+    Agentic,
+}
+
+impl InsightGenerationType {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::Standard => "standard",
+            Self::Agentic => "agentic",
+        }
+    }
+}
+
+impl ToString for InsightGenerationType {
+    fn to_string(&self) -> String {
+        self.as_str().to_string()
+    }
+}
+
+impl InsightGenerationType {
+    pub fn from_str(s: &str) -> Self {
+        match s {
+            "standard" => Self::Standard,
+            "agentic" => Self::Agentic,
+            _ => Self::Standard,
+        }
+    }
+}
+
 #[derive(Insertable)]
 #[diesel(table_name = users)]
 pub struct InsertUser<'a> {
@@ -394,3 +466,30 @@ pub struct VideoPreviewClip {
     pub created_at: String,
     pub updated_at: String,
 }
+
+#[derive(Insertable)]
+#[diesel(table_name = insight_generation_jobs)]
+pub struct InsertInsightGenerationJob {
+    pub library_id: i32,
+    #[diesel(column_name = file_path)]
+    pub path: String,
+    #[diesel(column_name = generation_type)]
+    pub gen_type: String,
+    pub status: String,
+    pub started_at: i64,
+}
+
+#[derive(Queryable, Serialize, Clone, Debug)]
+pub struct InsightGenerationJob {
+    pub id: i32,
+    pub library_id: i32,
+    #[diesel(column_name = file_path)]
+    pub path: String,
+    #[diesel(column_name = generation_type)]
+    pub gen_type: String,
+    pub status: String,
+    pub started_at: i64,
+    pub completed_at: Option<i64>,
+    pub result_insight_id: Option<i32>,
+    pub error_message: Option<String>,
+}