Fix: the settings page's membership block could show a stuck loading state with a broken QR image placeholder when no API key was configured — the CSS rules backing the plugin's is-hidden visibility toggles were missing from styles.css, so hide/show logic silently did nothing. Rules are now defined (element-qualified, no global selectors). Also removes a dead helper. Verified on Obsidian 1.13.4 with a full settings-page operability audit: 52 controls across all sections (including message-merge / image-localization / diary-link sub-sections), 24 text fields probed with real input events, zero inoperable controls; API-key entry through the UI and a real article pull re-verified.