feat: Implement comprehensive admin panel with CSV import system

- Add ImportLog model for tracking import history and results
- Create admin.html template with file upload form and progress display
- Implement POST /admin/upload route for CSV file handling with validation
- Build CSV import engine with dispatcher routing by filename patterns:
  * ROLODEX*.csv → Client model import
  * PHONE*.csv → Phone model import with client linking
  * FILES*.csv → Case model import
  * LEDGER*.csv → Transaction model import
  * QDROS*.csv → Document model import
  * PAYMENTS*.csv → Payment model import
- Add POST /admin/import/{data_type} route for triggering imports
- Implement comprehensive validation, error handling, and progress tracking
- Support for CSV header validation, data type conversions, and duplicate handling
- Real-time progress tracking with ImportLog database model
- Responsive UI with Bootstrap components for upload and results display
- Enhanced navigation with admin panel link already in place
- Tested import functionality with validation and error handling

The admin panel enables bulk importing of legacy CSV data from the old-csv/ directory, making the system fully functional with real data.

app/models.py

@@ -182,3 +182,29 @@ class Payment(Base):
 
     def __repr__(self):
         return f"<Payment(id={self.id}, amount={self.amount})>"
+
+
+class ImportLog(Base):
+    """
+    ImportLog model for tracking CSV import operations.
+
+    Records the history and results of bulk data imports from legacy CSV files.
+    """
+    __tablename__ = "import_logs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    import_type = Column(String(50), nullable=False)  # client, phone, case, transaction, document, payment
+    file_name = Column(String(255), nullable=False)
+    file_path = Column(String(500), nullable=False)
+    status = Column(String(20), default="pending")  # pending, running, completed, failed
+    total_rows = Column(Integer, default=0)
+    processed_rows = Column(Integer, default=0)
+    success_count = Column(Integer, default=0)
+    error_count = Column(Integer, default=0)
+    error_details = Column(Text)  # JSON string of error details
+    started_at = Column(DateTime(timezone=True), server_default=func.now())
+    completed_at = Column(DateTime(timezone=True))
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    def __repr__(self):
+        return f"<ImportLog(id={self.id}, type='{self.import_type}', status='{self.status}')>"