feat: implement internationalization for UI text, refactor localStorage keys, and add input validation for state setters.

src/constants.js

@@ -1,10 +1,54 @@
-export const API_BASE = 'https://api.bessa.app/v1';
-export const GUEST_TOKEN = 'c3418725e95a9f90e3645cbc846b4d67c7c66131';
-export const CLIENT_VERSION = 'v1.6.11';
-export const VENUE_ID = 591;
-export const MENU_ID = 7;
-export const POLL_INTERVAL_MS = 5 * 60 * 1000; // 5 minutes
+/**
+ * Application-wide constants.
+ * All API endpoints, IDs and timing parameters are centralized here
+ * to make changes easy and avoid magic numbers scattered across the codebase.
+ */
 
+/** Base URL for the Bessa REST API (v1). */
+export const API_BASE = 'https://api.bessa.app/v1';
+
+/** Guest token for unauthenticated API calls (e.g. browsing the menu). */
+export const GUEST_TOKEN = 'c3418725e95a9f90e3645cbc846b4d67c7c66131';
+
+/** The client version injected into every API request header. */
+export const CLIENT_VERSION = 'v1.6.16';
+
+/** Bessa venue ID for Knapp-Kantine. */
+export const VENUE_ID = 591;
+
+/** Bessa menu ID for the weekly lunch menu. */
+export const MENU_ID = 7;
+
+/** Polling interval for flagged-menu availability checks (5 minutes). */
+export const POLL_INTERVAL_MS = 5 * 60 * 1000;
+
+/** GitHub repository identifier for update checks and release links. */
 export const GITHUB_REPO = 'TauNeutrino/kantine-overview';
+
+/** GitHub REST API base URL for this repository. */
 export const GITHUB_API = `https://api.github.com/repos/${GITHUB_REPO}`;
+
+/** Base URL for htmlpreview-hosted installer pages. */
 export const INSTALLER_BASE = `https://htmlpreview.github.io/?https://github.com/${GITHUB_REPO}/blob`;
+
+/**
+ * Centralized localStorage key registry.
+ * Always use these constants instead of raw strings to avoid typos and ease renaming.
+ */
+export const LS = {
+    AUTH_TOKEN:              'kantine_authToken',
+    CURRENT_USER:            'kantine_currentUser',
+    FIRST_NAME:              'kantine_firstName',
+    LAST_NAME:               'kantine_lastName',
+    LANG:                    'kantine_lang',
+    FLAGS:                   'kantine_flags',
+    FLAGGED_LAST_CHECKED:    'kantine_flagged_items_last_checked',
+    LAST_CHECKED:            'kantine_last_checked',
+    MENU_CACHE:              'kantine_menuCache',
+    MENU_CACHE_TS:           'kantine_menuCacheTs',
+    HISTORY_CACHE:           'kantine_history_cache',
+    HIGHLIGHT_TAGS:          'kantine_highlightTags',
+    LAST_UPDATED:            'kantine_last_updated',
+    VERSION_CACHE:           'kantine_version_cache',
+    DEV_MODE:                'kantine_dev_mode',
+};