Reels pre-gen: record true media count + real upsert for user_ai_prefs

- pregen_one recorded media_count as planned.len() (beat count); record
  the actual media item total (media.len(), photos + clips) in both the
  cache-hit and freshly-rendered ledger paths. Drops the redundant
  photo_count binding.
- Replace upsert_prefs's insert-then-catch-error-then-update dance with a
  single atomic INSERT ... ON CONFLICT(id) DO UPDATE. Explicit id=1 makes
  the conflict target deterministic; explicit column .set((...)) keeps
  None -> NULL overwrite semantics so the row mirrors the latest request
  exactly, and genuine insert errors surface instead of being swallowed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/database/user_ai_prefs_dao.rs

@@ -84,21 +84,17 @@ impl UserAiPrefsDao for SqliteUserAiPrefsDao {
                 .lock()
                 .expect("Unable to lock UserAiPrefsDao");
 
-            // SQLite: INSERT on first call, UPDATE on subsequent calls.
-            // The first INSERT creates the row with id=1 (auto-increment).
-            // Subsequent calls UPDATE the existing row.
-            let result = diesel::insert_into(dsl::user_ai_prefs)
-                .values(prefs)
-                .execute(connection.deref_mut());
-
-            match result {
-                Ok(_) => {
-                    // First insert succeeded.
-                    Ok(())
-                }
-                Err(_e) => {
-                    // Insert failed (likely due to duplicate key). Update instead.
-                    diesel::update(dsl::user_ai_prefs.filter(dsl::id.eq(1)))
+            // Single-row table (id=1): one atomic upsert. The explicit id=1
+            // makes the conflict target deterministic so the second call
+            // updates in place rather than tripping the CHECK(id=1) constraint,
+            // and real insert errors surface instead of being swallowed into a
+            // separate update branch. The columns are set explicitly (rather
+            // than via AsChangeset) so a None field overwrites to NULL — the
+            // row mirrors the latest request exactly, not a merge of past ones.
+            diesel::insert_into(dsl::user_ai_prefs)
+                .values((dsl::id.eq(1), prefs))
+                .on_conflict(dsl::id)
+                .do_update()
                 .set((
                     dsl::voice.eq(&prefs.voice),
                     dsl::tz_offset_minutes.eq(&prefs.tz_offset_minutes),
@@ -108,8 +104,6 @@ impl UserAiPrefsDao for SqliteUserAiPrefsDao {
                 .execute(connection.deref_mut())
                 .map_err(|e| anyhow::anyhow!("Failed to upsert prefs: {}", e))?;
             Ok(())
-                }
-            }
         })
         .map_err(|e| DbError::log(DbErrorKind::InsertError, e))
     }

src/reels/mod.rs

@@ -1075,6 +1075,8 @@ async fn pregen_one(
     // Flatten every media item across beats (in order) into the cache key.
     let media: Vec<SegmentMedia> = planned.iter().flat_map(|b| b.media.clone()).collect();
     let key = cache_key(&selector, &media, voice.as_deref());
+    // Total media items shown (photos + clips), not beat count.
+    let media_count = media.len() as i32;
 
     // Dedup: check if fresh ledger row exists
     let now = std::time::SystemTime::now()
@@ -1127,7 +1129,7 @@ async fn pregen_one(
                 cache_key: key.clone(),
                 output_path: mp4_path.to_string_lossy().to_string(),
                 title,
-                media_count: planned.len() as i32,
+                media_count,
                 render_version: RENDER_VERSION as i32,
                 tz_offset_minutes: tz,
                 voice: voice.clone(),
@@ -1139,7 +1141,6 @@ async fn pregen_one(
 
     // Generate the reel
     log::info!("Generating precomputed reel for span={}, key={}", span, key);
-    let photo_count = planned.len() as i32;
     let (title, mp4) = produce_reel(
         app_state,
         insight_dao,
@@ -1163,7 +1164,7 @@ async fn pregen_one(
             cache_key: key.clone(),
             output_path: mp4.to_string_lossy().to_string(),
             title,
-            media_count: photo_count,
+            media_count,
             render_version: RENDER_VERSION as i32,
             tz_offset_minutes: tz,
             voice: voice.clone(),