[ chebizarro/nostrc ] docs: add comprehensive architecture documentation and Marmot API reference

Add detailed architecture overview covering the full monorepo structure:

ARCHITECTURE.md:
- Expand library table to include libmarmot, nostr-gobject, nostr-gtk, marmot-gobject with dependencies
- Add applications table (gnostr, gnostr-signer, relayd, relayctl, grelay)
- Add GNOME integration components table (GOA provider, Seahorse, PKCS#11, nostr-homed)
- Replace simple component diagram with comprehensive dependency graph showing
https://github.com/chebizarro/nostrc/commit/b437b30fabcd3990ea36b05ad51c4003bf357477