feat(cache): implement centralized caching layer for improved performance and reduced API calls

feat(microsoft-integration): enhance inbox and events fetching with caching support
feat(auth): include theme and notification settings in user data retrieval
feat(profile): improve password visibility toggle functionality
feat(planner): optimize event synchronization with Outlook using caching
fix(notifications): update mail badge handling for mobile and desktop

config/schema.sql

@@ -235,3 +235,10 @@ CREATE TABLE IF NOT EXISTS `jira_queue_filters` (
   `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
   `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS `app_cache` (
+  `cache_key` VARCHAR(128) NOT NULL PRIMARY KEY,
+  `cache_value` MEDIUMTEXT NOT NULL,
+  `expires_at` INT UNSIGNED NOT NULL,
+  INDEX `idx_app_cache_expires` (`expires_at`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;