Improve UI

- Add metrics table  to sidebar after schedule generation
- Add scheduler status indicator to sidebar
- Refactor report() to consume `ResidentMetrics`
- Delete unused preview component
- Beautify css across wizard steps

src-tauri/src/errors.rs

@@ -37,6 +37,8 @@ impl From<anyhow::Error> for SearchError {
 
 #[derive(Error, Debug)]
 pub enum ExportError {
+    #[error("no schedule has been generated yet")]
+    NotGenerated,
     #[error("path not found: {0}")]
     InvalidPath(#[from] io::Error),
     #[error("docx packaging error: {0}")]
@@ -57,6 +59,7 @@ impl Serialize for ExportError {
         s.serialize_field(
             "kind",
             match self {
+                ExportError::NotGenerated => "NotGenerated",
                 ExportError::InvalidPath(_) => "InvalidPath",
                 ExportError::Packaging(_) => "Packaging",
                 ExportError::OpenFailed(_) => "OpenFailed",