Fix: Keep ConfigPage tabs mounted to preserve form state

Previously, the tab content wrapper used 'key={tab}' which caused React to
unmount and remount the entire subtree when switching tabs. This destroyed
all component state, including unsaved form data and pending auto-saves.

Changes:
- Removed 'key={tab}' from the wrapper div
- All tab panels now render at page initialization
- Inactive tabs use CSS 'display: none' to hide without unmounting
- Tabs remain mounted throughout the page lifetime
- Users can now switch tabs without losing form input

Updated ConfigPage.test.tsx to reflect that inactive tabs remain in the DOM
(just hidden with CSS) rather than being removed entirely.

Documentation: Added 'Tab Panels' section to Web-Development.md
explaining the rule and rationale.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Docs/Tasks.md

@@ -1,15 +1,3 @@
-
-### ✅ TASK-BUG-01 — Infinite Re-Fetch Loop in `useJailConfigs` — DONE
-
-**Fix Summary**
-Wrapped the `onSuccess` callback in `useCallback` with empty dependencies in `frontend/src/hooks/useJailConfigs.ts` (lines 33-35). The inline callback was creating a new reference on every render, which caused `useListData`'s internal `refresh` function to be recreated (since `onSuccess` is in its deps), which triggered the `useEffect` again, causing an infinite fetch loop. 
-
-Added comprehensive test coverage in `frontend/src/hooks/__tests__/useJailConfigs.test.ts` to verify the hook no longer triggers infinite refetches. Updated `Docs/Refactoring.md` with documentation explaining the `onSuccess` stability requirement for all `useListData` callers.
-
-Commit: `de8af09a3da36dbf24b56fa28656673b232b5e91`
-
----
-
 ### TASK-BUG-02 — `ConfigPage` Tab Switch Destroys All Form State
 
 **Where found**
@@ -213,7 +201,6 @@ None required.
 **Why this is needed**
 Typing `"500"` in the Lines field currently fires three HTTP requests (`"5"`, `"50"`, `"500"`). Each request fetches potentially hundreds of log lines and serializes them, adding unnecessary backend load.
 
-
 ---
 
 ### TASK-ABORT-01 — Missing `signal` Parameter on Multiple API Functions

Docs/Web-Development.md

@@ -270,6 +270,12 @@ function BanCard({ isHighlighted }: BanCardProps): JSX.Element {
 - Supply a `key` prop whenever rendering lists — never use array indices as keys if the list can reorder.
 - Prefer Fluent UI components (`Button`, `Table`, `Input`, …) over raw HTML elements for any interactive or styled element.
 
+### Tab Panels
+
+- **Never** use `key` on a tab panel wrapper to switch between tabs. This causes the entire subtree to unmount and remount, destroying all state, pending saves, and form input.
+- Instead, render all tab panels and use CSS `display: none` / `display: block` to hide inactive tabs, keeping components mounted across tab switches.
+- All tab components remain mounted throughout the page lifetime. Hooks continue to run in hidden tabs — if a tab-specific effect must only run on activation, use an explicit activation flag rather than relying on mount/unmount.
+
 ```tsx
 import { Table, TableBody, TableRow, TableCell, Button } from "@fluentui/react-components";
 import type { Ban } from "../types/ban";

frontend/src/pages/ConfigPage.tsx

@@ -36,7 +36,11 @@ const useStyles = makeStyles({
   header: {
     marginBottom: tokens.spacingVerticalL,
   },
-  tabContent: {
+  tabPanel: {
+    display: "none",
+  },
+  tabPanelVisible: {
+    display: "block",
     marginTop: tokens.spacingVerticalL,
     animationName: "fadeInUp",
     animationDuration: tokens.durationNormal,
@@ -94,16 +98,26 @@ export function ConfigPage(): React.JSX.Element {
         <Tab value="regex">Regex Tester</Tab>
       </TabList>
 
-      <div className={styles.tabContent} key={tab}>
-        {tab === "jails" && (
+      <div className={tab === "jails" ? styles.tabPanelVisible : styles.tabPanel}>
         <JailsTab
           initialJail={(location.state as { jail?: string } | null)?.jail}
         />
-        )}
-        {tab === "filters" && <FiltersTab />}
-        {tab === "actions" && <ActionsTab />}
-        {tab === "server" && <ServerTab />}
-        {tab === "regex" && <RegexTesterTab />}
+      </div>
+
+      <div className={tab === "filters" ? styles.tabPanelVisible : styles.tabPanel}>
+        <FiltersTab />
+      </div>
+
+      <div className={tab === "actions" ? styles.tabPanelVisible : styles.tabPanel}>
+        <ActionsTab />
+      </div>
+
+      <div className={tab === "server" ? styles.tabPanelVisible : styles.tabPanel}>
+        <ServerTab />
+      </div>
+
+      <div className={tab === "regex" ? styles.tabPanelVisible : styles.tabPanel}>
+        <RegexTesterTab />
       </div>
     </div>
   );

frontend/src/pages/__tests__/ConfigPage.test.tsx

@@ -38,7 +38,8 @@ describe("ConfigPage", () => {
     renderPage();
     fireEvent.click(screen.getByRole("tab", { name: /filters/i }));
     expect(screen.getByTestId("filters-tab")).toBeInTheDocument();
-    expect(screen.queryByTestId("jails-tab")).not.toBeInTheDocument();
+    // Jails tab remains mounted (not removed from DOM), just hidden with CSS
+    expect(screen.getByTestId("jails-tab")).toBeInTheDocument();
   });
 
   it("switches to Actions tab when Actions tab is clicked", () => {