Zapier + Slack integration landing pages

/integrations/zapier ships six concrete prebuilt zap templates (red flag → Slack, WO completed → QuickBooks, hours → Sheets, urgent WO → SMS, tool failure → Slack, asset created → CMMS). /integrations/slack ships three Slack-native patterns from simplest (10-min Incoming Webhook) to richest (dedicated Slack App with /flag-resolve slash command).