Add central secrets file reference for API credentials

- Document ~/.secrets as the central credentials location
- Add usage examples for Gitea, Home Assistant, Syncthing, n8n
- List available credential variables

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -377,6 +377,31 @@ tests/
 
 Reference documentation: `~/Projects/homelab/`
 
+### API Credentials
+
+**Central secrets file**: `~/.secrets`
+
+```bash
+# Source credentials
+source ~/.secrets
+
+# Use in commands
+curl -H "Authorization: token $GITEA_TOKEN" https://git.htsn.io/api/v1/...
+curl -H "Authorization: Bearer $HA_TOKEN" $HA_URL/api/...
+curl -H "X-API-Key: $SYNCTHING_API_KEY_MACMINI" http://127.0.0.1:8384/rest/...
+curl -H "X-N8N-API-KEY: $N8N_API_KEY" $N8N_URL/api/v1/...
+```
+
+**Available credentials** (see `~/.secrets` for values):
+| Variable | Service | Purpose |
+|----------|---------|---------|
+| `GITEA_TOKEN` | Gitea | API access, repo creation |
+| `HA_TOKEN` | Home Assistant | Automation, sensors |
+| `SYNCTHING_API_KEY_*` | Syncthing | File sync status |
+| `N8N_API_KEY` | n8n | Workflow automation |
+| `CF_API_KEY` | Cloudflare | DNS management |
+| `TELEGRAM_BOT_TOKEN` | Telegram | Notifications |
+
 ### Servers
 
 | Server | IP | Specs | GPU | Purpose |