Add Kopia backup stack with Backblaze B2 offsite target.

Protects /config, selective labdata, and nightly DB dumps; documents homelab improvement plan briefs.

plans/homelab-improvements/tasks/TB-016-document-plex.md

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+# TB-016 — Document Plex
+
+**Status:** not started  
+**Your call:** _(unset — talk first)_
+
+---
+
+## Talk first
+
+> **Stop.** Don't read Reference until we've talked.
+> In chat, say **"let's do TB-016"** or **"document plex"**.
+
+**In one sentence:** Write down where Plex lives and how it connects to Tautulli — it's not in this repo.
+
+**Why it came up:** Tautulli reads /storage1/PMS logs but Plex isn't in compose; easy to forget how it's managed.
+
+### Questions
+
+1. Is Plex on valhalla itself, or another box?
+2. Do you want it in compose eventually, or happy as host-native?
+
+### Your options
+
+| Option | Meaning |
+|--------|---------|
+| **Do it** | We're doing this — I'll implement or walk you through it |
+| **Later** | Keep on the list, not now |
+| **Drop** | Remove from plan — totally fine |
+| **Tweak** | Change scope; tell me how |
+
+### What we decided
+
+| | |
+|---|---|
+| **Decision** | |
+| **Notes** | |
+| **Date** | |
+
+---
+
+<details>
+<summary>Reference (only open if we're doing it)</summary>
+
+### Stack / files
+
+Docs only
+
+### If we do it — rough steps
+
+1. You tell me: install path, systemd?, library paths
+2. Add short section to CLAUDE.md or EXTERNAL-SERVICES.md
+
+### Done when
+
+- [ ] Plex documented with paths
+
+</details>