fix: M4 Phase 1 bugs - dev.chunks refs, search_path, uuid column

Bug fixes from M4 report:
- 4 remaining dev.chunks → dev.chunk in SQL queries
- search_path includes public for pgvector extension
- get_chunk_by_chunk_id_and_uuid: uuid → file_uuid
- New endpoint: GET /api/v1/file/:uuid/chunk/:chunk_id

src/worker/job_worker.rs

@@ -1002,7 +1002,7 @@ impl JobWorker {
         let pool = db.pool();
 
         let rows = sqlx::query_as::<_, (String, String, String, f64, f64, String)>(
-            "SELECT chunk_id, chunk_type, text_content, start_time, end_time, content::text FROM dev.chunks WHERE file_uuid = $1 AND chunk_type = 'sentence' AND embedding IS NULL AND (text_content IS NOT NULL AND text_content != '') ORDER BY chunk_index",
+            "SELECT chunk_id, chunk_type, text_content, start_time, end_time, content::text FROM dev.chunk WHERE file_uuid = $1 AND chunk_type = 'sentence' AND embedding IS NULL AND (text_content IS NOT NULL AND text_content != '') ORDER BY id",
         )
         .bind(uuid)
         .fetch_all(pool)

src/worker/processor.rs

@@ -1080,7 +1080,7 @@ impl ProcessorPool {
                 "top_5": scene.top_5,
             });
             let _ = sqlx::query(
-                "UPDATE dev.chunks SET metadata = metadata || $1::jsonb WHERE file_uuid=$2 AND chunk_id=$3"
+                "UPDATE dev.chunk SET metadata = metadata || $1::jsonb WHERE file_uuid=$2 AND chunk_id=$3"
             )
             .bind(&meta)
             .bind(uuid)