feat: delete + deactivate for sites, zones, and trucks; harden incident API error handling

- zones: add active column (migration 20260713000005)
- sites/zones API: PATCH (toggle active) + DELETE (blocked when incidents reference it)
- trucks API: PATCH + DELETE with same pattern
- admin page: select active for sites + zones
- site-zone-manager + truck-manager: deactivate toggle + delete button per row with busyId
- incidents API: reject reports on deactivated zone/site; wrap handler in top-level try-catch so unhandled errors return JSON (not HTML)
- report-form: parse JSON separately so HTTP status code surfaces instead of generic "Something went wrong"

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

supabase/migrations/20260713000005_zones_active.sql

@@ -0,0 +1,4 @@
+-- Add soft-delete support to zones (sites and trucks already have this column).
+-- Leave zones_read as USING (true) so deactivated zones still render on historical incidents.
+-- Deactivation is enforced for new reports in the create-incident API, not via RLS.
+ALTER TABLE zones ADD COLUMN active BOOLEAN NOT NULL DEFAULT true;