feat: enhance Jira analytics with caching and force refresh

- Updated `getJiraAnalytics` to accept a `forceRefresh` parameter for optional cache bypass.
- Modified `getProjectAnalytics` to check the cache and return cached data unless forced to refresh.
- Adjusted `loadAnalytics` in `useJiraAnalytics` to trigger a forced refresh on manual updates.
- Improved UI in `JiraDashboardPageClient` to indicate when data is served from cache.

src/app/jira-dashboard/JiraDashboardPageClient.tsx

@@ -154,13 +154,20 @@ export function JiraDashboardPageClient({ initialJiraConfig }: JiraDashboardPage
                 ))}
               </div>
               
-              <Button
-                onClick={refreshAnalytics}
-                disabled={isLoading}
-                variant="secondary"
-              >
-                {isLoading ? '🔄 Actualisation...' : '🔄 Actualiser'}
-              </Button>
+              <div className="flex items-center gap-2">
+                {analytics && (
+                  <div className="text-xs text-[var(--muted-foreground)] px-2 py-1 bg-[var(--card)] border border-[var(--border)] rounded">
+                    💾 Données en cache
+                  </div>
+                )}
+                <Button
+                  onClick={refreshAnalytics}
+                  disabled={isLoading}
+                  variant="secondary"
+                >
+                  {isLoading ? '🔄 Actualisation...' : '🔄 Actualiser'}
+                </Button>
+              </div>
             </div>
           </div>