Fix: preserve quote context when author is null or invalid

[joeykrug]

Fixes #1935

Problem

When receiving a quoted/replied message, signal-cli silently drops the quote data if the quote author's ServiceId is null or fails the isValid() check. This means consumers of the signal-cli API (JSON-RPC, D-Bus) never receive quote context for these messages.

The root cause is an overly strict .filter() on the quote Optional in MessageEnvelope.java that discards the entire quote when the author can't be resolved, rather than preserving the quote with a fallback author.

Fix

1. Remove the .filter(q -> q.getAuthor() != null && q.getAuthor().isValid()) that drops quotes entirely
2. In Quote.from(), handle null/invalid authors by falling back to RecipientAddress.UNKNOWN_UUID
3. Use Optional.ofNullable() for quote text (defensive)

Testing

This fix has been tested in production with a source-built 0.14.0-SNAPSHOT:

• Message delivery works normally (two checkmarks)
• Quote/reply context now flows through to JSON-RPC consumers
• No regressions in message sending or receiving

[joeykrug]

Closing due to other PR being a cleaner way to do this and more comprehensive