Searchable dropdown (#2312)

* Searchable dropdown

* format fix

* Refactor SearchableDropdown with Fluent UI components, extract styles, and add tests (#2329)

* Initial plan

* Refactor SearchableDropdown with Fluent UI components and add tests

- Replace native HTML elements with Fluent UI components (Stack, DefaultButton, Text)
- Extract inline styles to SearchableDropdown.styles.ts
- Add comprehensive unit tests (14 test cases)
- Verify behavior consistency with AccountSwitcher tests

Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

* Optimize SearchableDropdown with useMemo for filteredItems

Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

* Fix text alignment to match original UI - ensure left alignment

- Add flexContainer.justifyContent: "flex-start" to button styles
- Add textAlign: "left" to button label, item styles, and empty message
- Restore original left-aligned appearance for placeholder and selected text

Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

* Fix TypeScript implicit type errors in SearchableDropdown tests (#2355)

* Initial plan

* Fix TypeScript compilation errors in SearchableDropdown.test.tsx

Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: nishthaAhujaa <45535788+nishthaAhujaa@users.noreply.github.com>

* ui fixes minor

* format fix

* added search icon and updated the text

* removed callbacks

* added mocked playwright data

* fixed formatting

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Co-authored-by: nishthaAhujaa <nishtha17354@iiittd.ac.in>
Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Sakshi Gupta <sakshig@microsoft.com>
Co-authored-by: sakshigupta12feb <sakshigupta12feb1@gmail.com>

src/Common/SearchableDropdown.styles.ts

@@ -0,0 +1,78 @@
+import { IButtonStyles, IStackStyles, ITextStyles } from "@fluentui/react";
+import * as React from "react";
+
+export const getDropdownButtonStyles = (disabled: boolean): IButtonStyles => ({
+  root: {
+    width: "100%",
+    height: "32px",
+    padding: "0 28px 0 8px",
+    border: "1px solid #8a8886",
+    background: "#fff",
+    color: "#323130",
+    textAlign: "left",
+    cursor: disabled ? "not-allowed" : "pointer",
+    position: "relative",
+  },
+  flexContainer: {
+    justifyContent: "flex-start",
+  },
+  label: {
+    fontWeight: "normal",
+    fontSize: "14px",
+    textAlign: "left",
+  },
+});
+
+export const buttonLabelStyles: ITextStyles = {
+  root: {
+    overflow: "hidden",
+    textOverflow: "ellipsis",
+    whiteSpace: "nowrap",
+    display: "block",
+    textAlign: "left",
+  },
+};
+
+export const buttonWrapperStyles: React.CSSProperties = {
+  position: "relative",
+  width: "100%",
+};
+
+export const chevronStyles: React.CSSProperties = {
+  position: "absolute",
+  right: "8px",
+  top: "50%",
+  transform: "translateY(-50%)",
+  pointerEvents: "none",
+  fontSize: "12px",
+};
+
+export const calloutContentStyles: IStackStyles = {
+  root: {
+    display: "flex",
+    flexDirection: "column",
+  },
+};
+
+export const listContainerStyles: IStackStyles = {
+  root: {
+    maxHeight: "300px",
+    overflowY: "auto",
+  },
+};
+
+export const getItemStyles = (isSelected: boolean): React.CSSProperties => ({
+  padding: "8px 12px",
+  cursor: "pointer",
+  fontSize: "14px",
+  backgroundColor: isSelected ? "#e6e6e6" : "transparent",
+  textAlign: "left",
+});
+
+export const emptyMessageStyles: ITextStyles = {
+  root: {
+    padding: "8px 12px",
+    color: "#605e5c",
+    textAlign: "left",
+  },
+};