wiki: add Tailscale SSH reauth article; update Netdata Docker alarm tuning (50 articles)

- New: Tailscale SSH unexpected re-authentication prompt — diagnosis and fix
- Updated: netdata-docker-health-alarm-tuning — add delay: up 3m to suppress
  Nextcloud AIO PHP-FPM ~90s startup false alerts; update settings table and notes
- Updated: 05-troubleshooting/index.md and SUMMARY.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

05-troubleshooting/networking/tailscale-ssh-reauth-prompt.md

@@ -0,0 +1,66 @@
+# Tailscale SSH: Unexpected Re-Authentication Prompt
+
+If a Tailscale SSH connection unexpectedly presents a browser authentication URL mid-session, the first instinct is to check the ACL policy. However, this is often a one-off Tailscale hiccup rather than a misconfiguration.
+
+## Symptoms
+
+- SSH connection to a fleet node displays a Tailscale auth URL:
+  ```
+  To authenticate, visit: https://login.tailscale.com/a/xxxxxxxx
+  ```
+- The prompt appears even though the node worked fine previously
+- Other nodes in the fleet connect without prompting
+
+## What Causes It
+
+Tailscale SSH supports two ACL `action` values:
+
+| Action | Behavior |
+|---|---|
+| `accept` | Trusts Tailscale identity — no additional auth required |
+| `check` | Requires periodic browser-based re-authentication |
+
+If `action: "check"` is set, every session (or after token expiry) will prompt for browser auth. However, even with `action: "accept"`, a one-off prompt can appear due to a Tailscale daemon glitch or key refresh event.
+
+## How to Diagnose
+
+### 1. Verify the ACL policy
+
+In the Tailscale admin console (or via `tailscale debug acl`), inspect the SSH rules. For a trusted homelab fleet, the rule should use `accept`:
+
+```json
+{
+    "src":    ["autogroup:member"],
+    "dst":    ["autogroup:self"],
+    "users":  ["autogroup:nonroot", "root"],
+    "action": "accept",
+}
+```
+
+If `action` is `check`, that is the root cause — change it to `accept` for trusted source/destination pairs.
+
+### 2. Confirm it was a one-off
+
+If the ACL already shows `accept`, the prompt was transient. Test with:
+
+```bash
+ssh <hostname> "echo ok"
+```
+
+No auth prompt + `ok` output = resolved. Note that this test is only meaningful if the previous session's auth token has expired, or you test from a different device that hasn't recently authenticated.
+
+## Fix
+
+**If ACL shows `check`:** Change to `accept` in the Tailscale admin console under Access Controls. Takes effect immediately — no server changes needed.
+
+**If ACL already shows `accept`:** No action required. The prompt was a one-off Tailscale event (daemon restart, key refresh, etc.). Monitor for recurrence.
+
+## Notes
+
+- Port 2222 on **MajorRig** exists as a hard bypass for Tailscale SSH browser auth — regular SSH over Tailscale network, bypassing Tailscale SSH entirely. This is an alternative approach if `check` mode is required for compliance but browser auth is too disruptive.
+- The `autogroup:self` destination means the rule applies when connecting from your own devices to your own devices — appropriate for a personal homelab fleet.
+
+## Related
+
+- [[Network Overview]] — Tailscale fleet inventory and SSH access model
+- [[SSH-Aliases]] — Fleet SSH access shortcuts