Host the manual's images in the repo under manual/images (#6861)

* Host the manual's images in the repo under manual/images

Replaces all learn.omacom.io/manual.omakub.org hotlinks with local webp
files capped at 1600px wide (~20MB total), so the manual is fully
self-contained. Theme and unlock previews are converted from the
canonical themes/*/preview.png files. A handful of illustration shots
are interim conversions of the current images, pending retakes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Retake the illustration screenshots fresh at 3x scaling

Navigation, clipboard history, notices, tmux layouts, prompt, and About
reshot on a clean workspace at 3.13x (1920x1080 logical on 6K) across
ten themes: Tokyo Night, Catppuccin, Gruvbox, Kanagawa, Everforest,
Nord, Osaka Jade, Rose Pine, Matte Black, and Ristretto.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Drop the extra themes chapter from the manual

The community theme gallery will live elsewhere. Removes the chapter
and its 114 gallery images, renumbers the following chapters, and
repoints the two references (theme installs still work via
Install > Style > Theme in the menu).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Reference the shipped theme previews instead of copying them

The themes chapter now points straight at themes/*/preview.png and
preview-unlock.png, so previews can never drift from the source and
manual/images drops from 6.3MB to 3.5MB.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

manual/35-networking.md

@@ -30,7 +30,7 @@ _Trigger > Speed Test > Network Speed Test_ measures your actual up and down spe
 
 The firewall is on by default and blocks all incoming traffic, with one exception: port 53317, so [LocalSend](22-guis.md) works out of the box.
 
-SSH is off until you turn it on with _Setup > Security > SSHD_, which starts the daemon, opens port 22 rate-limited against brute force, and authorizes a key. Docker is locked down too, so containers can't accidentally expose themselves to the world. See [security](49-security.md) for the whole story.
+SSH is off until you turn it on with _Setup > Security > SSHD_, which starts the daemon, opens port 22 rate-limited against brute force, and authorizes a key. Docker is locked down too, so containers can't accidentally expose themselves to the world. See [security](48-security.md) for the whole story.
 
 ## Tailscale
 
@@ -42,4 +42,4 @@ Installing it also adds a web app for the Tailscale admin console.
 
 ## When it stops working
 
-Before rebooting, try restarting the offending piece on its own. _Update > Hardware_ has Wi-Fi, Bluetooth, Audio, and Trackpad, and reloading one of those clears up most "it worked five minutes ago" situations. See [troubleshooting](46-troubleshooting.md).
+Before rebooting, try restarting the offending piece on its own. _Update > Hardware_ has Wi-Fi, Bluetooth, Audio, and Trackpad, and reloading one of those clears up most "it worked five minutes ago" situations. See [troubleshooting](45-troubleshooting.md).