[ eskema/alphaama ] Add aa.signer abstraction for NIP-07/NIP-46, db-only queries, update nostr-tools

- Introduce aa.signer layer wrapping window.nostr (nip07) and BunkerSigner (nip46)
  with unified signEvent, getPublicKey, nip04/nip44 encrypt/decrypt
- Support bunker:// URLs in u setup, persist bunker state for reconnection across reloads
- Replace all window.nostr calls with aa.signer across fx/nostr, e/clk, e/e, e/mk, b/b
- Add db:save bus event for persisting events to redstore via manager worker
- Remove unused aa.clk.post, remove 'post' from not_sent actions
- Add db-only query mode: .q req db {filter} queries redstore without relay roundtrip
- Prevent 'db' as relay set name since it's now reserved
https://github.com/eskema/alphaama/commit/698e3c881382651a3d0fc8b2c56c24252b9e0be7