Implement dashboard and audit log templates, add paginated audit log support

- Added `web/templates/{dashboard,audit,base,accounts,account_detail}.html` for a consistent UI.
- Implemented new audit log endpoint (`GET /v1/audit`) with filtering and pagination via `ListAuditEventsPaged`.
- Extended `AuditQueryParams`, added `AuditEventView` for joined actor/target usernames.
- Updated configuration (`goimports` preference), linting rules, and E2E tests.
- No logic changes to existing APIs.

internal/crypto/crypto_test.go

@@ -27,7 +27,10 @@ func TestGenerateEd25519KeyPair(t *testing.T) {
 	}
 
 	// Public key must be extractable from private key.
-	derived := priv1.Public().(ed25519.PublicKey)
+	derived, ok := priv1.Public().(ed25519.PublicKey)
+	if !ok {
+		t.Fatal("priv1.Public() did not return ed25519.PublicKey")
+	}
 	if !bytes.Equal(derived, pub1) {
 		t.Error("public key derived from private key does not match generated public key")
 	}