Freeze Hub inbound API v1; choose Go for the service

- docs/hub-api.md: language decision (Go 1.25) with reason and the
  frozen v1 routes POST /ask, POST /approve, GET /health, including
  request/response schemas, bearer-token auth, timeouts, error shapes,
  logging, versioning, and a safety confirmation that no route is a
  high-consequence control.
- Update README, hub_brief.md open items, and the outline docs so they
  no longer say the API is undecided or the language is open.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

docs/outline/02-config-and-env.md

@@ -17,6 +17,11 @@ Relevant keys:
 | `OL_API_KEY` | Outline docs. |
 | `VIKUNJA_TOKEN` | Vikunja tasks. |
 | `GITEA_TOKEN` | Gitea repository. |
+| `HUB_TOKEN_PHONE` | Hub token for the phone app. |
+| `HUB_TOKEN_ESP32` | Hub token for the house voice. |
+| `HUB_TOKEN_DSH` | Hub token for dsh chat. |
+| `HUB_TOKEN_CONSOLE` | Hub token for the console portal. |
+| `HUB_TOKEN_ADMIN` | Hub token for the admin app. The only trusted door. |
 
 ## Services and Ports
 
@@ -28,7 +33,7 @@ Relevant keys:
 | Home Assistant | 192.168.20.30 | 8123 | Devices and timers. |
 | MQTT | 192.168.20.13 | 1883 | Voice topics. |
 | Apprise | 192.168.20.35 | 8210 | Notifications. |
-| Hub | not allocated | — | This service. |
+| Hub | 192.168.20.13 | 8787 | This service. Proposed default (`HUB_PORT`). |
 
 ## Config Paths