docs(admin): admin-guide front door + Administration area in the portal

The tenth and final page: the section directory with one-line coverage
per page, the fresh-instance quick path (libraries -> scan -> Base URL
-> users -> devices), and the when-something-looks-wrong triage table
mapping symptoms to pages. The portal (index.md) gains a For
Administrators area listing all nine admin pages; the user guide's
'being expanded separately' line becomes the done-state sentence.
Every control name quoted here exists in the glossary.

docs/admin/admin-guide.md

@@ -1,16 +1,54 @@
+<!-- Ground truth: the Administration section itself (docs/admin/), the app
+     sidebar's Administration group (templates/header.templ: Dashboard,
+     Libraries, Podcasts, Hash Conflicts, Users, Settings), and the
+     per-page ground-truth comments in this directory. This page is a
+     directory; the pages it links to carry their own source pins. -->
+
 # Admin Guide
 
-**Coming Soon**
+Everything an instance administrator runs lives in this section. Like the
+rest of Bookhoard's docs, pages tell you what to click — but admin pages
+add the layer users don't need: **what each control actually does** before
+you click it, what it costs, and what it changes. (The calibration, if
+you're curious: *user docs = what you see, admin docs = what it does,
+developer docs = how it works*.)
 
-This guide will cover:
+## The Administration section
 
-- User management
-- Library management
-- System monitoring
-- Analytics and reporting
-- Security settings
-- Backup and restore
+| Page | What it covers |
+| --- | --- |
+| [Dashboard](dashboard.md) | The `/admin` landing page: stats, file-watcher status, **Force Rescan All Libraries**, live scan progress |
+| [Libraries](libraries.md) | Creating libraries, folders, per-user visibility, per-library scans, deletion semantics |
+| [Processing Issues](library-processing-issues.md) | Per-library ledger of items the scanner couldn't process — Retry, Retry all, Dismiss |
+| [Archived Items](archived-items.md) | The missing-file lifecycle: two-strikes archiving, Merge/Restore/Delete, retention |
+| [Podcasts](podcasts.md) | The all-feeds maintenance view: disk usage, refresh, delete files, remove for everyone |
+| [Hash Conflicts](hash-conflicts.md) | Byte-identical duplicates and their resolution (merge reading data or keep both) |
+| [Users](users.md) | Accounts, roles, password resets, the last-admin guards |
+| [Settings](settings.md) | Every server-wide setting: key, default, range, what it does, restart or live |
+| [Scanning](scanning.md) | The deep-dive: shallow vs. force, and what every scan button actually does |
 
----
+The app's own sidebar shows the first six as the **Administration** group;
+Processing Issues and Archived Items hang off the Libraries page.
 
-_In the meantime, check out our [Operations Portal](../operations/operations.md)_
+## If you're setting up a fresh instance
+
+The shortest sane path, in order:
+
+1. **[Libraries](libraries.md)** → Create Library, add its folders
+2. Let the initial scan populate it (or **Force Rescan** to be sure)
+3. **[Settings](settings.md)** → set the **Base URL** to the address other
+   devices will use, and check **Auto-Scan** is on
+4. **[Users](users.md)** → create accounts (or leave public registration
+   on), set roles
+5. Point devices at the server — the [device guides](../user/user-guide.md)
+   walk each one
+
+## When something looks wrong
+
+- Books vanished from the library? [Archived Items](archived-items.md) —
+  they're almost certainly there, history intact.
+- A book's metadata is stale or wrong? Open the book → **Rescan**
+  (re-extracts that one item, sidecars included).
+- Duplicates? [Hash Conflicts](hash-conflicts.md).
+- A scan didn't pick up your changes? [Scanning](scanning.md) explains
+  which scans skip unchanged files — and which never do.