rebrand: Switchboard Core → Armature

- Rename Go module switchboard-core → armature (155+ files)
- Rename Docker image → gobha/armature
- Rename K8s resources, secrets, deployments
- Rename Prometheus metrics switchboard_* → armature_*
- Rename env vars SWITCHBOARD_ADMIN_* → ARMATURE_ADMIN_*
- Rename DB names switchboard_core* → armature*
- Update all frontend branding, notification templates, docs
- Update CI scripts, e2e tests, Keycloak realm, nginx conf
- Rename scripts/switchboard-ca.sh → scripts/armature-ca.sh
- Rename k8s/switchboard.yaml → k8s/armature.yaml
- Rename chart alerting/dashboard files
- Fix: DockerHub push uses env: binding for secret injection
- Helm chart updated (name, labels, template functions, dashboard, alerting)
- Replace favicon/icon assets with Armature brand

No functional changes. Pure mechanical rename + CI fix.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/TUTORIAL-FIRST-EXTENSION.md

@@ -1,9 +1,9 @@
 # Build Your First Browser Extension
 
 This tutorial walks through building a browser extension that renders custom
-code blocks, modeled on the CSV Table Viewer that ships with Switchboard.
+code blocks, modeled on the CSV Table Viewer that ships with Armature.
 
-**Prerequisites:** A running Switchboard instance, a text editor, and `zip`.
+**Prerequisites:** A running Armature instance, a text editor, and `zip`.
 
 ## Step 1: Create the Directory