fix(addon): resolve all Odoo 18 install errors

- security/res_groups.xml: fully qualify ref('group_ai_user') with module prefix
- data/ir_cron.xml: remove numbercall field (removed in Odoo 17/18)
- views/menus.xml: remove web_icon referencing missing static/src/img/icon.png
- controllers/webhook.py: use get_json() instead of deprecated json.loads(data)
- security/ir.model.access.csv: use fully-qualified group external IDs (prior commit)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/activeblue_ai/views/menus.xml

@@ -3,7 +3,6 @@
     <menuitem id="menu_activeblue_ai_root"
               name="ActiveBlue AI"
               sequence="99"
-              web_icon="activeblue_ai,static/src/img/icon.png"
               groups="activeblue_ai.group_ai_user"/>
 
     <menuitem id="menu_ai_directives"