Retry insight persistence with exponential backoff to avoid SQLite lock contention

Add retry_with_backoff utility (100ms base, ±25% jitter, 3 attempts)
and replace all 11 direct DAO calls in insight_chat.rs and
insight_generator.rs. The Mutex guard drops between retries so the
maintenance connection can release its SQLite write lock.

src/ai/insight_generator.rs

@@ -26,7 +26,7 @@ use crate::libraries::Library;
 use crate::memories::extract_date_from_filename;
 use crate::otel::global_tracer;
 use crate::tags::TagDao;
-use crate::utils::{earliest_fs_time, normalize_path};
+use crate::utils::{earliest_fs_time, normalize_path, retry_with_backoff};
 
 /// Max location records rendered by `tool_get_location_history`. The DAO
 /// query is range-bounded, not limited, so the tool caps the rendered list
@@ -1539,10 +1539,13 @@ impl InsightGenerator {
             eval_count: None,
         };
 
-        let mut dao = self.insight_dao.lock().expect("Unable to lock InsightDao");
-        let result = dao
-            .store_insight(&insight_cx, insight)
-            .map_err(|e| anyhow::anyhow!("Failed to store insight: {:?}", e));
+        let dao = self.insight_dao.clone();
+        let result = retry_with_backoff("store_insight", 3, || {
+            let cx = opentelemetry::Context::new();
+            let mut d = dao.lock().expect("Unable to lock InsightDao");
+            d.store_insight(&cx, insight.clone())
+        })
+        .map_err(|e| anyhow::anyhow!("Failed to store insight: {:?}", e));
 
         match &result {
             Ok(_) => {
@@ -4465,11 +4468,13 @@ Return ONLY the summary, nothing else."#,
             eval_count: last_eval_count,
         };
 
-        let stored = {
-            let mut dao = self.insight_dao.lock().expect("Unable to lock InsightDao");
-            dao.store_insight(&insight_cx, insight)
-                .map_err(|e| anyhow::anyhow!("Failed to store agentic insight: {:?}", e))
-        };
+        let dao = self.insight_dao.clone();
+        let stored = retry_with_backoff("store_insight", 3, || {
+            let cx = opentelemetry::Context::new();
+            let mut d = dao.lock().expect("Unable to lock InsightDao");
+            d.store_insight(&cx, insight.clone())
+        })
+        .map_err(|e| anyhow::anyhow!("Failed to store agentic insight: {:?}", e));
 
         match &stored {
             Ok(_) => {