Indexing: Fix post-scan reconciler "DB is locked"

- The replay connection was opened with `open_write_connection`, contending with the writer thread's exclusive write lock in WAL mode
- Changed to `open_read_connection` — the reconciler only reads (path resolution), all writes go through the writer channel
- This also prevented `scan_completed_at` from being persisted (early return on error), causing a full rescan on every restart

Author: vdavid

apps/desktop/src-tauri/src/indexing/mod.rs

@@ -622,7 +622,7 @@ impl IndexManager {
                     });
 
                     // Open a read connection for path resolution during replay
-                    let replay_conn = match IndexStore::open_write_connection(&writer.db_path()) {
+                    let replay_conn = match IndexStore::open_read_connection(&writer.db_path()) {
                         Ok(c) => c,
                         Err(e) => {
                             log::warn!("Reconciler: failed to open read connection for replay: {e}");