feat: Seamless sleep/wake screens for displaying book pages during deep sleep (#2064)

<img width="605" height="454" alt="image"
src="https://github.com/user-attachments/assets/bfd84afe-3b58-436e-9a5d-539af3ec3d4e"
/>

Actualized "Last" sleep screen setting from previous PRs, rebranded as a
~~`Seamless Sleep`~~ `Page as Sleep Screen` option with more
improvements.


https://github.com/user-attachments/assets/59029ba6-007e-4841-abfa-f680d7e98b79

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New option: `Page as Sleep Screen` - `Never (default)`, `After Timeout`,
`Always`

When enabled, it seamlessly sleeps on timeout or power off, making a
fast refresh for the moon icon. When waking up, we still show the last
page, instead of the boot screen, making it fully seamless.

I tried different icons such as "refresh arrow" and others, but they
looked not as nice as 3 simple dots.

With this mode, the device turns off 4 seconds faster. And has 6 seconds
less delay when turning back on. Much more responsive.

Previously, even a 10-minute timeout sometimes wasn't enough, and I'd
worry about seeing the book cover. It's now easier to use a shorter
sleep timeout: if I get distracted during a reading session but don't
want to stop, the new screen is much more inviting to come back to.

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Did you use AI tools to help write this code? _**PARTIALLY**_.

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Test v1.3.0 firmware.bin file
[download](https://github.com/user-attachments/files/28015193/firmware.zip)

Based on PRs #410 and #495

Closes #400, #1649

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/I18n/translations/english.yaml

@@ -62,6 +62,8 @@ STR_CAT_READER: "Reader"
 STR_CAT_CONTROLS: "Controls"
 STR_CAT_SYSTEM: "System"
 STR_SLEEP_SCREEN: "Sleep Screen"
+STR_SEAMLESS_SLEEP: "Page as Sleep Screen"
+STR_AFTER_TIMEOUT: "After Timeout"
 STR_SLEEP_COVER_MODE: "Sleep Screen Cover Mode"
 STR_HIDE_BATTERY: "Hide Battery %"
 STR_EXTRA_SPACING: "Extra Paragraph Spacing"