Implement DDD refactoring phases 1-4 with domain layer and ubiquitous language

Phase 1-3: Domain Layer Foundation
- Add value objects: IdentityId, PermissionId, RelayId, WalletId, Nickname, NostrKeyPair
- Add rich domain entities: Identity, Permission, Relay with behavior
- Add domain events: IdentityCreated, IdentityRenamed, IdentitySelected, etc.
- Add repository interfaces for Identity, Permission, Relay
- Add infrastructure layer with repository implementations
- Add EncryptionService abstraction

Phase 4: Ubiquitous Language Cleanup
- Rename BrowserSyncData → EncryptedVault (encrypted vault storage)
- Rename BrowserSessionData → VaultSession (decrypted session state)
- Rename SignerMetaData → ExtensionSettings (extension configuration)
- Rename Identity_ENCRYPTED → StoredIdentity (storage DTO)
- Rename Identity_DECRYPTED → IdentityData (session DTO)
- Similar renames for Permission, Relay, NwcConnection, CashuMint
- Add backwards compatibility aliases with @deprecated markers

Test Coverage
- Add comprehensive tests for all value objects
- Add tests for domain entities and their behavior
- Add tests for domain events
- Fix PermissionChecker to prioritize kind-specific rules over blanket rules
- Fix pre-existing component test issues (IconButton, Pubkey)

All 113 tests pass. Both Chrome and Firefox builds succeed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

projects/firefox/src/app/common/data/firefox-meta-handler.ts

@@ -1,5 +1,5 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
-import { SignerMetaData, SignerMetaHandler } from '@common';
+import { ExtensionSettings, SignerMetaHandler } from '@common';
 import browser from 'webextension-polyfill';
 
 export class FirefoxMetaHandler extends SignerMetaHandler {
@@ -20,7 +20,7 @@ export class FirefoxMetaHandler extends SignerMetaHandler {
     return data;
   }
 
-  async saveFullData(data: SignerMetaData): Promise<void> {
+  async saveFullData(data: ExtensionSettings): Promise<void> {
     await browser.storage.local.set(data as Record<string, any>);
     console.log(data);
   }