Per-device tokens with revocation (issue #11)

Auth previously used the shared IRIS_TOKEN as the security principal:
a leaked token meant access to all devices, and a compromised device
could not be isolated.

Gateway:
- pairing.py: devices.token column (in-place migration) + revoked
  denylist table; issue_token (idempotent, 64 hex), token_for,
  reissue_token, revoke/unrevoke/is_revoked/list_revoked. The token
  never leaks into device dicts (push fan-out / listings).
- http_server.py: auth accepts the shared token (bootstrap/legacy) OR
  the device's own token (both constant-time); a revoked device_id is
  rejected with 401 before either comparison. On SSE open (pairing)
  the per-device token is minted and returned in hello.ack.
- protocol.py: hello_ack(..., device_token).
- adapter.py: setup flow (hermes gateway setup -> Iris) now offers
  'Remove a paired device?' on an existing setup: numbered select
  menu (last option = exit the removal loop), confirmation, back to
  the menu for further removals.
- tools/iris_devices.py: operator CLI (list / revoke / unrevoke /
  reissue), stdlib only.

App:
- SecureStore.deviceToken (Android: EncryptedSharedPreferences;
  Desktop: second keyring slot iris-device-token / device_token.enc).
- HelloAckPayload.deviceToken; GatewayClient stores it on hello and
  presents it instead of the shared token from then on (live provider
  in HttpGateway); savePairing/clear wipe it for re-pairing.

Docs: 09 §9.3 stretch -> implemented (revocation semantics, both
control surfaces), 04 hello.ack example, frames.schema.json, M7 row 13.

Tests: 8 new Python tests (issuance, acceptance, revocation,
isolation, unrevoke, registry unit x2, setup-flow menu) - 94/94 pass;
2 new Kotlin wire tests - green. Live-verified against a running
gateway (hello.ack token matches devices.db; revoke -> 401 even with
shared token; unrevoke -> 200; setup TUI both paths).

docs/protocol/frames.schema.json

@@ -24,6 +24,7 @@
           "server_caps": { "type": "object", "properties": { "streaming": {"type":"boolean"}, "reasoning": {"type":"boolean"}, "tools": {"type":"boolean"}, "media": {"type":"boolean"}, "search": {"type":"boolean"}, "push": {"type":"string","enum":["fcm","ntfy","none"]}, "push_ntfy_server": {"type":"string","description":"ntfy server URL for the app's listener; empty string when the backend is not ntfy."}, "pickers": {"type":"boolean"} } },
           "sync_cursor": { "type": "integer" },
           "last_pushed_cursor": { "type": "integer", "description": "Highest outbox cursor already delivered to THIS device via the push backend (0 = never). The app skips system notifications for sync-replayed frames at/below it (dedupe, docs/08 §8.7)." },
+          "device_token": { "type": "string", "description": "Per-device token minted at pairing (docs/09 §9.3). The app stores it and presents it INSTEAD of the shared IRIS_TOKEN from then on; the gateway can revoke it per device. Empty when the gateway didn't issue one (legacy)." },
           "channels": { "type": "array", "items": { "$ref": "#/definitions/channel" } }
         }
       },