fix: stop swallowing DB errors across the entire DAO layer

Every map_err(|_| DbError::new(...)) and map_err(|_| anyhow!("..."))
in the database layer was discarding the actual Diesel/SQLite error,
making failures impossible to diagnose from logs.

- Add DbError::log() that logs the source error before converting
- Replace all ~130 swallowed outer map_err closures with DbError::log
- Replace all ~47 swallowed inner anyhow closures to include the
  source error in the message

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/database/location_dao.rs

@@ -273,7 +273,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
                 source_file: location.source_file,
             })
         })
-        .map_err(|_| DbError::new(DbErrorKind::InsertError))
+        .map_err(|e| DbError::log(DbErrorKind::InsertError, e))
     }
 
     fn store_locations_batch(
@@ -350,7 +350,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
 
             Ok(inserted)
         })
-        .map_err(|_| DbError::new(DbErrorKind::InsertError))
+        .map_err(|e| DbError::log(DbErrorKind::InsertError, e))
     }
 
     fn find_nearest_location(
@@ -385,7 +385,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
 
             Ok(results.into_iter().next().map(|r| r.to_location_record()))
         })
-        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+        .map_err(|e| DbError::log(DbErrorKind::QueryError, e))
     }
 
     fn find_locations_in_range(
@@ -413,7 +413,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
             .map(|rows| rows.into_iter().map(|r| r.to_location_record()).collect())
             .map_err(|e| anyhow::anyhow!("Query error: {:?}", e))
         })
-        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+        .map_err(|e| DbError::log(DbErrorKind::QueryError, e))
     }
 
     fn find_locations_near_point(
@@ -468,7 +468,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
 
             Ok(filtered)
         })
-        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+        .map_err(|e| DbError::log(DbErrorKind::QueryError, e))
     }
 
     fn location_exists(
@@ -502,7 +502,7 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
 
             Ok(result.count > 0)
         })
-        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+        .map_err(|e| DbError::log(DbErrorKind::QueryError, e))
     }
 
     fn get_location_count(&mut self, context: &opentelemetry::Context) -> Result<i64, DbError> {
@@ -525,6 +525,6 @@ impl LocationHistoryDao for SqliteLocationHistoryDao {
 
             Ok(result.count)
         })
-        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+        .map_err(|e| DbError::log(DbErrorKind::QueryError, e))
     }
 }