feat: OCR independent chunks (方案 A) + stats API

Rule 1 now creates OCR chunks separately from ASRX segments:
- Phase 1: ASRX segments (pure speech, NO OCR merge)
- Phase 2: OCR-only chunks (all OCR frames grouped by proximity)

Added OCR statistics to ingestion status API:
- rule1_ocr: shows OCR pre_chunks count
- rule1_ocr_chunks: shows OCR-only chunks count

Example: FilmRiot_test now has 32 ASRX + 3 OCR-only = 35 chunks
Stats: rule1_sentence: 35, rule1_ocr: 30, rule1_ocr_chunks: 3

src/api/scan.rs

@@ -508,6 +508,17 @@ async fn get_ingestion_status(
         "SELECT COUNT(*) FROM {chunk} WHERE file_uuid = '{file_uuid}' AND chunk_type = 'sentence'"
     ));
     let sentence_embedded = count_sql!(&format!("SELECT COUNT(*) FROM {chunk} WHERE file_uuid = '{file_uuid}' AND chunk_type = 'sentence' AND embedding IS NOT NULL"));
+
+    // OCR statistics
+    let pre_chunks_table = schema::table_name("pre_chunks");
+    let ocr_pre_chunks: i64 = count_sql!(&format!(
+        "SELECT COUNT(*) FROM {pre_chunks_table} WHERE file_uuid = '{file_uuid}' AND processor_type = 'ocr'"
+    ));
+    let ocr_only_chunks: i64 = count_sql!(&format!(
+        "SELECT COUNT(*) FROM {chunk} WHERE file_uuid = '{file_uuid}' AND chunk_type = 'sentence' \
+         AND (content->>'text' = '' OR content->>'text' IS NULL) \
+         AND content->>'ocr_text' IS NOT NULL AND content->>'ocr_text' != ''"
+    ));
     let scene_count = count_sql!(&format!(
         "SELECT COUNT(*) FROM {chunk} WHERE file_uuid = '{file_uuid}' AND chunk_type = 'cut'"
     ));
@@ -595,6 +606,16 @@ async fn get_ingestion_status(
             sentence_count > 0,
             Some(format!("{sentence_count} sentence chunks"))
         ),
+        step!(
+            "rule1_ocr",
+            ocr_pre_chunks > 0,
+            Some(format!("{ocr_pre_chunks} OCR frames"))
+        ),
+        step!(
+            "rule1_ocr_chunks",
+            ocr_only_chunks > 0,
+            Some(format!("{ocr_only_chunks} OCR-only chunks"))
+        ),
         step!(
             "auto_vectorize",
             sentence_embedded > 0,