Feature/delta team/epic r04 (#7)

## Summary

epic r04 - begin refactor

## Change Type

- [x] Cowork feature
- [ ] Bug fix
- [ ] Core AI contribution
- [ ] Test / hardening
- [ ] Performance
- [ ] Documentation

## Related Work

Cowork Task:

Core Repo: http://34.143.229.138/gitea-admin/fsg-ai-core-assets

Core AI Issue:

Core Task:

Related PR:

## Scope

What is intentionally included?

What is intentionally NOT included?

## Validation

- [ ] Unit tests
- [ ] Integration tests
- [ ] Manual verification
- [ ] Regression check

Commands / evidence:

## Security Impact

Permission / credential / network / customer data impact:

## Compatibility

- [ ] No breaking change
- [ ] Breaking change documented

## Reviewer Notes

Anything Cowork reviewers should pay attention to.

---------

Co-authored-by: Anh Tran Nguyen Minh <anhtnm1@fpt.com>
Co-authored-by: Huong Le Thi Thien <huongltt35@fpt.com>
Co-authored-by: Nam Pham Dinh Thanh <nampdt@fpt.com>
Co-authored-by: Vu Dam Tuan <vudt15@fpt.com>
Co-authored-by: Hiep Ha Van <hiephv3@fpt.com>
Co-authored-by: Lam Hoang Van <lamhv7@fpt.com>
Reviewed-on: #7
Co-authored-by: Duy Le Huu <duylh19@fpt.com>

presentation/scheduling/ai_task_import_dialog.py

@@ -0,0 +1,157 @@
+"""Import-from-file tab content for AI Create Task (R08-T11, extracted from
+``ui/schedule_task_tab.py``'s ``_AiCreateDialog`` — the Import tab + its
+``_DropZone``, lines 551-576/643-665/674-720 of the original file).
+
+:class:`ImportTaskPanel` is a plain ``QWidget`` (not its own dialog) so
+``ai_task_creator_dialog.py`` can embed it as one tab of the single AI-create
+dialog the user sees — the two files are a code split, not a UX split; there
+is still one dialog with two tabs, exactly as before.
+"""
+from __future__ import annotations
+
+from pathlib import Path
+from typing import List
+
+from PySide6.QtCore import Signal
+from PySide6.QtWidgets import (
+    QHBoxLayout, QLabel, QMessageBox, QPlainTextEdit, QPushButton,
+    QVBoxLayout, QWidget,
+)
+
+from cowork_local.application.scheduling.ai_task_planner_service import (
+    AiTaskPlannerService,
+)
+from cowork_local.i18n import tr
+from cowork_local.theme import current_palette
+from cowork_local.ui.icons import icon
+from cowork_local.ui.osutil import open_path
+
+
+class _DropZone(QLabel):
+    """Drag-an-.xlsx-here area for the Import tab."""
+
+    file_dropped = Signal(str)
+
+    def __init__(self):
+        """Vùng kéo–thả tệp danh sách task."""
+        super().__init__()
+        from PySide6.QtCore import Qt
+
+        self.setAlignment(Qt.AlignCenter)
+        self.setMinimumHeight(70)
+        _p = current_palette()
+        self.setStyleSheet(
+            f"QLabel {{ border: 1px dashed {_p.border_strong};"
+            f" border-radius: {_p.radius_lg}px;"
+            f" color: {_p.text_muted}; padding: 10px; }}")
+        self.setAcceptDrops(True)
+
+    def dragEnterEvent(self, event):  # noqa: N802
+        """Chỉ nhận tệp có đuôi hợp lệ."""
+        urls = event.mimeData().urls()
+        if urls and urls[0].toLocalFile().lower().endswith(
+                (".xlsx", ".xlsm", ".xls", ".csv", ".json")):
+            event.acceptProposedAction()
+
+    def dropEvent(self, event):  # noqa: N802
+        """Thả tệp: phát đường dẫn lên để panel đọc và dựng danh sách task."""
+        urls = event.mimeData().urls()
+        if urls:
+            self.file_dropped.emit(urls[0].toLocalFile())
+
+
+class ImportTaskPanel(QWidget):
+    """Pick/drag an Excel/CSV/JSON file, preview the tasks it maps to, and
+    hold that NOT-yet-saved list — the dialog reads :attr:`planned` when the
+    user confirms.
+
+    Args:
+        planner: an ``AiTaskPlannerService`` — ``import_file`` is called
+            through it (R07-T05) rather than ``core.task_import`` directly.
+    """
+
+    tasks_changed = Signal(bool)   # True when the current preview has >=1 valid task
+
+    def __init__(self, planner: AiTaskPlannerService, parent=None):
+        """Panel nhập task từ tệp: xuất mẫu, chọn tệp, xem trước rồi mới tạo."""
+        super().__init__(parent)
+        self._planner = planner
+        self.planned: List[dict] = []
+
+        il = QVBoxLayout(self)
+        tpl_btn = QPushButton(tr("schedtask.export_template_btn"))
+        tpl_btn.setIcon(icon("upload"))
+        tpl_btn.clicked.connect(self._export_template)
+        il.addWidget(tpl_btn)
+        pick_row = QHBoxLayout()
+        pick_btn = QPushButton(tr("schedtask.import_pick_btn"))
+        pick_btn.setIcon(icon("folder"))
+        pick_btn.clicked.connect(self._pick_import_file)
+        pick_row.addWidget(pick_btn)
+        pick_row.addStretch(1)
+        il.addLayout(pick_row)
+        self.drop_zone = _DropZone()
+        self.drop_zone.setText(tr("schedtask.drop_hint"))
+        self.drop_zone.file_dropped.connect(self._load_import_file)
+        il.addWidget(self.drop_zone)
+        il.addWidget(QLabel(tr("schedtask.ai_preview_label")))
+        self.preview = QPlainTextEdit()
+        self.preview.setReadOnly(True)
+        il.addWidget(self.preview, 1)
+
+    def _export_template(self) -> None:
+        """Xuất file mẫu Excel để người dùng điền danh sách task rồi nhập lại."""
+        from PySide6.QtWidgets import QFileDialog
+
+        from cowork_local.core.task_excel import export_template
+
+        path, _ = QFileDialog.getSaveFileName(
+            self, tr("schedtask.export_template_btn"),
+            "cowork_tasks_template.xlsx", "Excel (*.xlsx)")
+        if not path:
+            return
+        try:
+            export_template(path)
+            open_path(str(Path(path).parent))
+        except Exception as exc:  # noqa: BLE001
+            QMessageBox.warning(self, tr("schedtask.tab_import"), str(exc))
+
+    def _pick_import_file(self) -> None:
+        """Chọn file danh sách task để nhập."""
+        from PySide6.QtWidgets import QFileDialog
+
+        from cowork_local.core.task_import import IMPORT_FILTER
+
+        path, _ = QFileDialog.getOpenFileName(
+            self, tr("schedtask.import_pick_btn"), "", IMPORT_FILTER)
+        if path:
+            self._load_import_file(path)
+
+    def _load_import_file(self, path: str) -> None:
+        """Đọc file và dựng danh sách task xem trước; file sai khuôn thì hiện lý do cụ
+        thể chứ không im lặng bỏ qua.
+        """
+        try:
+            self.planned = self._planner.import_file(path)
+        except ValueError as exc:
+            # Same as the original single-class dialog: a bad file leaves
+            # whatever was previously loaded in `planned` untouched (only the
+            # preview text and the Ok button reflect the failure) rather than
+            # discarding a prior successful load.
+            self.preview.setPlainText(str(exc))
+            self.tasks_changed.emit(False)
+            return
+        by_id = {t["task_id"]: t["title"] for t in self.planned}
+        lines = []
+        for i, t in enumerate(self.planned, 1):
+            sched = t.get("schedule", {})
+            when = sched.get("run_at") if sched.get("enabled") else tr("schedtask.no_schedule")
+            deps = t.get("dependency", {}).get("depends_on") or []
+            dep_note = ("  ← depends: " + ", ".join(by_id.get(d, "?") for d in deps)) if deps else ""
+            lines.append(f"{i}. [{t.get('task_type')}] {t.get('title')}\n"
+                         f"    {when}   repeat={sched.get('repeat_type', 'none')}{dep_note}")
+        self.preview.setPlainText("\n\n".join(lines))
+        self.tasks_changed.emit(bool(self.planned))
+
+
+__all__ = ["ImportTaskPanel"]