fix(csv): unwrap export force-text markers

crates/dbx-core/src/table_import.rs

@@ -492,8 +492,29 @@ pub fn effective_delimited_config(
     })
 }
 
+/// Undo the `="..."` force-text wrapper that CSV export writes around temporal
+/// cells (see `temporal_format::wrap_csv_force_text`). Without this, exporting a
+/// table with a datetime column and importing the file straight back stores the
+/// literal `="2026-06-24 02:00:07"` instead of the timestamp, which every
+/// temporal column type then rejects.
+///
+/// Only the exact wrapper shape is unwrapped: a leading `="`, a trailing `"`,
+/// and no `"` in between. A genuine value that merely starts with `=` (or
+/// contains quotes of its own) is left untouched, so this cannot corrupt CSV
+/// files that dbx did not produce.
+fn unwrap_csv_force_text(value: &str) -> &str {
+    let Some(inner) = value.strip_prefix("=\"").and_then(|rest| rest.strip_suffix('"')) else {
+        return value;
+    };
+    if inner.contains('"') {
+        return value;
+    }
+    inner
+}
+
 pub fn csv_value_with_config(value: &str, config: DelimitedParseConfig) -> serde_json::Value {
     let value = if config.trim_values { value.trim() } else { value };
+    let value = unwrap_csv_force_text(value);
     if config.empty_string_as_null && value.is_empty() {
         serde_json::Value::Null
     } else {
@@ -9690,6 +9711,60 @@ mod tests {
         assert_eq!(text_batches[0].sql, "INSERT INTO \"issue_6491\" (\"amount\") VALUES\n('1,234.56'),\n('12,345')");
     }
 
+    #[test]
+    fn csv_import_unwraps_the_force_text_wrapper_written_by_csv_export() {
+        // Export wraps temporal cells as `="..."` so spreadsheets stop re-typing
+        // them; re-importing that file has to produce the plain timestamp again.
+        let parsed = parse_csv_bytes(b"insert_time,id\n\"=\"\"2026-06-24 02:00:07\"\"\",695350\n", 10).unwrap();
+
+        assert_eq!(parsed.rows[0][0], serde_json::Value::String("2026-06-24 02:00:07".to_string()));
+        assert_eq!(parsed.rows[0][1], serde_json::Value::String("695350".to_string()));
+
+        let mappings = vec![
+            TableImportColumnMapping {
+                source_column: "insert_time".to_string(),
+                target_column: "insert_time".to_string(),
+                target_data_type: None,
+            },
+            TableImportColumnMapping {
+                source_column: "id".to_string(),
+                target_column: "id".to_string(),
+                target_data_type: None,
+            },
+        ];
+        let batches = build_import_insert_batches(
+            &parsed,
+            &mappings,
+            &[("insert_time".to_string(), "datetime".to_string()), ("id".to_string(), "bigint".to_string())],
+            "issue_8803",
+            "",
+            &DatabaseType::Mysql,
+            500,
+        )
+        .unwrap();
+
+        assert_eq!(
+            batches[0].sql,
+            "INSERT INTO `issue_8803` (`insert_time`, `id`) VALUES\n('2026-06-24 02:00:07', 695350)"
+        );
+    }
+
+    #[test]
+    fn csv_import_keeps_values_that_only_look_like_the_force_text_wrapper() {
+        // Formula-looking data that dbx did not write must survive untouched,
+        // otherwise importing a third-party CSV silently rewrites its cells.
+        let parsed = parse_csv_bytes(
+            b"expr\n\"=\"\"a\"\"&\"\"b\"\"\"\n=SUM(A1:A2)\n\"=\"\"unterminated\"\n\"just \"\"quoted\"\" text\"\n",
+            10,
+        )
+        .unwrap();
+
+        assert_eq!(parsed.rows[0][0], serde_json::Value::String("=\"a\"&\"b\"".to_string()));
+        assert_eq!(parsed.rows[1][0], serde_json::Value::String("=SUM(A1:A2)".to_string()));
+        assert_eq!(parsed.rows[2][0], serde_json::Value::String("=\"unterminated".to_string()));
+        assert_eq!(parsed.rows[3][0], serde_json::Value::String("just \"quoted\" text".to_string()));
+    }
+
     #[test]
     fn formats_only_excel_columns_mapped_to_text_targets() {
         let path = std::env::temp_dir().join(format!("dbx-table-import-display-formats-{}.xlsx", uuid::Uuid::new_v4()));