Complete tasks 1-5: UI cleanup, pie chart fix, log path allowlist, activation hardening

Task 1: Remove ActiveBansSection from JailsPage
- Delete buildBanColumns, fmtTimestamp, ActiveBansSection
- Remove Dialog/Delete/Dismiss imports, ActiveBan type
- Update JSDoc to reflect three sections

Task 2: Remove JailDistributionChart from Dashboard
- Delete import and JSX block from DashboardPage.tsx

Task 3: Fix transparent pie chart (TopCountriesPieChart)
- Add Cell import and per-slice <Cell fill={slice.fill}> children inside <Pie>
- Suppress @typescript-eslint/no-deprecated (recharts v3 types)

Task 4: Allow /config/log as safe log prefix
- Add '/config/log' to _SAFE_LOG_PREFIXES in config_service.py
- Update error message to list both allowed directories

Task 5: Block jail activation on missing filter/logpath
- activate_jail refuses to proceed when filter/logpath issues found
- ActivateJailDialog treats all validation issues as blocking
- Trigger immediate _run_probe after activation in config router
- /api/health now reports fail2ban online/offline from cached probe
- Add TestActivateJailBlocking tests; fix existing tests to mock validation

frontend/src/components/TopCountriesPieChart.tsx

@@ -4,6 +4,7 @@
  */
 
 import {
+  Cell,
   Legend,
   Pie,
   PieChart,
@@ -177,7 +178,12 @@ export function TopCountriesPieChart({
               return `${name}: ${(percent * 100).toFixed(0)}%`;
             }}
             labelLine={false}
-          />
+          >
+            {slices.map((slice, index) => (
+              // eslint-disable-next-line @typescript-eslint/no-deprecated
+              <Cell key={index} fill={slice.fill} />
+            ))}
+          </Pie>
           <Tooltip content={PieTooltip} />
           <Legend formatter={legendFormatter} />
         </PieChart>