feat(photon): gRPC-native iMessage channel (no webhook)

Make Photon iMessage a first-class persistent-connection channel like
Discord/Slack, using the spectrum-ts gRPC stream for both directions.

- Inbound: the sidecar forwards the SDK's app.messages gRPC stream to the
  adapter over a loopback GET /inbound (NDJSON) instead of webhooks. Drops
  the aiohttp webhook server, HMAC signature verification, public URL, and
  PHOTON_WEBHOOK_* config; adapter reconnects with backoff.
- Management plane: device login uses client_id=photon-cli against the
  single dashboard host (Bearer), matching the official photon-hq/cli;
  find-or-create "Hermes Agent" project, enable Spectrum, rotate secret,
  register user (with phone dedup), surface the assigned iMessage line.
- SDK projectId is the project's spectrumProjectId, not the dashboard id;
  runtime creds persist to ~/.hermes/.env like every other channel.
- CLI: 6-step setup, webhook subcommands removed.
- Tests/docs updated for the gRPC flow; sidecar pins spectrum-ts ^1.17.1.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/platforms/photon/sidecar/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@hermes-agent/photon-sidecar",
   "private": true,
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "Spectrum-ts bridge for the Hermes Agent Photon platform plugin.",
   "type": "module",
   "main": "index.mjs",
@@ -12,6 +12,6 @@
     "node": ">=18.17"
   },
   "dependencies": {
-    "spectrum-ts": "^0.1.0"
+    "spectrum-ts": "^1.17.1"
   }
 }