Add root README with architecture diagram, .env.example for all products

products/.env.example

@@ -0,0 +1,37 @@
+# dd0c Environment Variables
+# Copy to .env and fill in your values
+
+# --- Shared ---
+DATABASE_URL=postgresql://dd0c:dd0c-dev@localhost:5432/dd0c_alert
+REDIS_URL=redis://localhost:6379
+JWT_SECRET=change-me-to-a-real-secret-at-least-32-chars
+CORS_ORIGIN=*
+LOG_LEVEL=info
+PORT=3000
+
+# --- P1: route ---
+# OPENAI_API_KEY=sk-...
+# ANTHROPIC_API_KEY=sk-ant-...
+
+# --- P3: alert ---
+# DATADOG_WEBHOOK_SECRET=...
+# PAGERDUTY_WEBHOOK_SECRET=...
+# OPSGENIE_WEBHOOK_SECRET=...
+
+# --- P4: portal ---
+# MEILI_URL=http://localhost:7700
+# MEILI_KEY=...
+# GITHUB_TOKEN=ghp_...
+
+# --- P5: cost ---
+# AWS_ACCESS_KEY_ID=...
+# AWS_SECRET_ACCESS_KEY=...
+# ANOMALY_THRESHOLD=50
+
+# --- P6: run ---
+# SLACK_BOT_TOKEN=xoxb-...
+# SLACK_SIGNING_SECRET=...
+
+# --- Notifications (shared) ---
+# SLACK_WEBHOOK_URL=https://hooks.slack.com/services/...
+# RESEND_API_KEY=re_...