docs: add full wiki with 74 pages, assets, and CI workflow

Adds the complete TREK documentation wiki covering installation,
trip planning, admin panel, MCP/AI integration, addons, and operations.

Also fixes encrypt-at-rest gaps: mapbox_access_token, Synology
credentials, per-user webhook/ntfy tokens, and photo passphrases
are now rotated by migrate-encryption.ts and stored encrypted via
settingsService.

wiki/Admin-Categories.md

@@ -0,0 +1,47 @@
+# Admin — Categories
+
+The **Personalization** tab → **Categories** section lets you manage global place categories. Categories are shared across all trips and all users on the instance.
+
+<!-- TODO: screenshot: category list in admin panel -->
+
+![Category Manager](assets/CategoryManager.png)
+
+## What categories are
+
+A category is a label consisting of a name, a color, and an icon. Users assign categories to places when creating or editing a place. Categories appear:
+
+- In the place form's category selector
+- As colored chips on place cards
+- In the places filter panel
+- In the map legend
+
+## Creating a category
+
+Click **New Category** (top-right of the category section). A form appears inline:
+
+1. **Name** — required. Free-text label for the category.
+2. **Icon** — a scrollable grid of ~47 curated Lucide icons (Pin, Hotel, Restaurant, Transport, Nature, etc.). Click any icon to select it. The default icon is `MapPin`.
+3. **Color** — 12 preset color swatches plus a custom color picker (pipette button). The default color is `#6366f1` (indigo). The 12 presets are:
+
+   `#6366f1` · `#8b5cf6` · `#ec4899` · `#ef4444` · `#f97316` · `#f59e0b` · `#10b981` · `#06b6d4` · `#3b82f6` · `#84cc16` · `#6b7280` · `#1f2937`
+
+4. A **live preview** chip shows how the category will appear to users as you make selections.
+
+Click **Create** to save.
+
+## Editing a category
+
+Click the pencil icon on any category row. The same form appears in-place with the existing values pre-filled. Change any field and click **Update**.
+
+## Deleting a category
+
+Click the trash icon on a category row and confirm. Deletion sets `category_id` to `NULL` on any places that had the category assigned — the places themselves are not affected, they become uncategorized.
+
+## List ordering
+
+Categories are always displayed in alphabetical order by name. There is no manual reordering.
+
+## Related pages
+
+- [Places-and-Search](Places-and-Search)
+- [Admin-Panel-Overview](Admin-Panel-Overview)