Added explicit detection for NIP-04 encrypted content format:
- NIP-04: base64 content with ?iv= suffix
- NIP-44: detected by Helpers.hasHiddenContent()
- Encrypted tags: detected by Helpers.hasHiddenTags()
Created hasEncryptedContent() helper that checks all three cases.
Now properly shows padlock emoji and decrypt button for events with
NIP-04 encrypted content (like the example with ?iv=5KzDXv09...).