fix: BLE entities unavailable after deep-sleep wakeup; configurable upload queue expiry

[Copilot]

Summary:
This PR fixes a real-world deep-sleep wakeup issue for BLE OpenDisplay tags and makes deep-sleep upload handling explicit and configurable.

The key user-visible problem was: when tags woke and advertised as non-connectable, entities could remain unavailable and sensor-driven automations would not reliably trigger.

Main functional changes:

1. BLE availability fix for wakeup advertisements
   OpenDisplayBLEEntity.available now checks presence with connectable=False.
   This ensures tags are considered available when they wake and emit non-connectable advertisements.
   Result: sensor entities come back reliably and automations can trigger on wakeup updates.
2. Deep-sleep upload queue (behavior + lifecycle)
   A dedicated DeepSleepUploadQueue is used for sleeping tags so uploads are not lost or sent at the wrong time.

How it works:

1. Upload request arrives for a tag.
2. Integration checks whether tag is currently sleeping in deep-sleep mode.
3. If sleeping, upload is queued per tag instead of sent immediately.
4. On tag check-in/wakeup signal, queued upload is moved into normal upload flow and executed.

Replacement semantics (important)
Queue is intentionally single-slot per tag:

• If a new upload is queued for the same tag while one is already pending, the old one is replaced by the newest one.
• This keeps behavior deterministic and avoids stale/obsolete images being sent after wake.
• Maintainers get predictable “last write wins” semantics for sleeping devices.

Expiration semantics

• Pending deep-sleep uploads expire after a configurable timeout.
• Default timeout is 4 hours.
• Expired items are dropped to prevent very old payloads being uploaded after long sleep gaps.

3. Options Flow support for queue expiry
   Added integration option for deep-sleep queue expiry hours.
   Range is validated/clamped (1–24h).
   Default remains 4h.

About the broader file diff

This branch includes a few small cleanup/refactor edits outside strict deep-sleep code paths (for example removing unused imports/unused locals in some files).

These are low-risk, no-behavior-change cleanups and are left in the PR intentionally to keep the branch history intact. The deep-sleep behavior changes are still concentrated in:

• custom_components/opendisplay/upload.py
• custom_components/opendisplay/services.py
• custom_components/opendisplay/coordinator.py
• custom_components/opendisplay/config_flow.py
• custom_components/opendisplay/entity.py
• custom_components/opendisplay/const.py
• tests/test_deep_sleep_queue.py
• tests/test_ble_entity_available.py

Test coverage
Deep-sleep queue tests

tests/test_deep_sleep_queue.py verifies:

• replacement of existing pending upload for same tag
• default expiry behavior (4h)
• configurable expiry behavior
• wake/check-in flush into active upload queue
• queue decision logic for sleeping vs awake tags

Availability regression tests
tests/test_ble_entity_available.py verifies:

• entity availability check uses connectable=False
• non-connectable-only presence marks entity available
• unavailable remains correct when device is not seen

Why this should be merged

• Fixes a user-facing reliability issue (wakeups not reflected in HA availability/sensors).
• Prevents stale deep-sleep uploads by design (single-slot replacement + expiry).
• Adds operator control via Options Flow instead of hardcoded behavior.
• Includes targeted tests for both queue semantics and BLE availability regression.