feat: Add report templates API for CRUD operations and implement SLM settings modal

- Implemented a new API router for managing report templates, including endpoints for listing, creating, retrieving, updating, and deleting templates.
- Added a new HTML partial for a unified SLM settings modal, allowing users to configure SLM settings with dynamic modem selection and FTP credentials.
- Created a report preview page with an editable data table using jspreadsheet, enabling users to modify report details and download the report as an Excel file.

backend/models.py

@@ -278,3 +278,25 @@ class DataFile(Base):
     file_metadata = Column(Text, nullable=True)  # JSON
 
     created_at = Column(DateTime, default=datetime.utcnow)
+
+
+class ReportTemplate(Base):
+    """
+    Report templates: saved configurations for generating Excel reports.
+    Allows users to save time filter presets, titles, etc. for reuse.
+    """
+    __tablename__ = "report_templates"
+
+    id = Column(String, primary_key=True, index=True)  # UUID
+    name = Column(String, nullable=False)  # "Nighttime Report", "Full Day Report"
+    project_id = Column(String, nullable=True)  # Optional: project-specific template
+
+    # Template settings
+    report_title = Column(String, default="Background Noise Study")
+    start_time = Column(String, nullable=True)  # "19:00" format
+    end_time = Column(String, nullable=True)    # "07:00" format
+    start_date = Column(String, nullable=True)  # "2025-01-15" format (optional)
+    end_date = Column(String, nullable=True)    # "2025-01-20" format (optional)
+
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)