chore: reduce workflow cron frequencies (#1046)

- discovery: every 30 min → every 3 days
- refactor: every 5 min → hourly
- security: every 5 min → every 30 min

Co-authored-by: Security Reviewer <security-reviewer@spawn.dev>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/discovery.yml

@@ -2,7 +2,7 @@ name: Trigger Discovery
 
 on:
   schedule:
-    - cron: '*/30 * * * *'
+    - cron: '0 0 */3 * *'
   issues:
     types: [opened, reopened, labeled]
   workflow_dispatch:

.github/workflows/refactor.yml

@@ -2,7 +2,7 @@ name: Trigger Refactor
 
 on:
   schedule:
-    - cron: '*/5 * * * *'
+    - cron: '0 * * * *'
   issues:
     types: [opened, reopened, labeled]
   workflow_dispatch:

.github/workflows/security.yml

@@ -4,7 +4,7 @@ on:
   issues:
     types: [opened, reopened, labeled]
   schedule:
-    - cron: '*/5 * * * *'
+    - cron: '*/30 * * * *'
   workflow_dispatch:
 
 concurrency: