feat: add Last Used timestamp sensor per code slot

[tykeal]

Summary

Adds a per-code-slot "Last Used" timestamp sensor that records when each PIN code was last used to unlock. The sensor resets to None when the slot is reset, and only tracks usage on the specific lock (not coupled to parent locks).

Changes

• lock.py: Added last_used: dt | None = None field to KeymasterCodeSlot and type lookup
• coordinator.py: Set last_used timestamp in _lock_unlocked() for valid code slots (slot > 0)
• sensor.py: Create per-slot KeymasterSensor with SensorDeviceClass.TIMESTAMP via entity description in async_setup_entry
• lovelace.py: Insert "Last Used" entity between "Active" and "Sync Status" in both regular and parent view cards
• test_sensor.py: 6 new tests for last-used sensor behavior + updated entity counts
• test_coordinator.py: 4 new tests (set on unlock, not set for slot 0, parent not updated, cleared on reset)
• test_lovelace.py: Added last_used to expected entity patterns
• test_init.py: Refactored to baseline counting with KEYMASTER_SENSOR_COUNT constant for cross-version compatibility

Design Decisions

• last_used is per-lock only — unlike accesslimit_count (shared budget), usage timestamps are observational data
• Only unlock events track code usage (lock events don't carry code_slot_num)
• reset_code_slot() replaces the entire KeymasterCodeSlot instance, so last_used defaults to None automatically

[Copilot]

Pull request overview

Adds per-code-slot “Last Used” timestamp tracking and exposes it as a Home Assistant timestamp sensor, so users can see when each PIN slot was last used to unlock.

Changes:

• Add last_used: datetime | None to KeymasterCodeSlot and set it on unlock events for valid (non-zero) code slots.
• Add a per-slot KeymasterLastUsedSensor (SensorDeviceClass.TIMESTAMP) and include it in setup.
• Update Lovelace card generation and test expectations to include the new entity, plus add coordinator/sensor test coverage.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
custom_components/keymaster/lock.py	Adds last_used to the code slot model and type lookup for persistence/serialization.
custom_components/keymaster/coordinator.py	Sets last_used on unlock for the used code slot and triggers coordinator updates.
custom_components/keymaster/sensor.py	Creates per-slot last-used sensors and defines the new sensor entity class.
custom_components/keymaster/lovelace.py	Inserts “Last Used” entity into code slot cards (regular + parent view).
tests/test_sensor.py	Updates entity creation counts and adds targeted tests for last-used sensor behavior.
tests/test_coordinator.py	Adds tests verifying last_used is set/reset correctly and not propagated to parent locks.
tests/test_lovelace.py	Updates expected generated Lovelace entity list to include last_used.
tests/test_init.py	Updates sensor entity count expectations for integration setup/unload/remove.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.45%. Comparing base (cdb4922) to head (d3e7ba0).
⚠️ Report is 64 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #585      +/-   ##
==========================================
+ Coverage   84.14%   88.45%   +4.31%     
==========================================
  Files          10       26      +16     
  Lines         801     3145    +2344     
==========================================
+ Hits          674     2782    +2108     
- Misses        127      363     +236     

Flag	Coverage Δ
python	88.45% <100.00%> (?)

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[Copilot]

Pull request overview

Adds a per-code-slot “Last Used” timestamp sensor to the Keymaster integration, updating coordinator state on unlock events and surfacing the value in generated Lovelace views.

Changes:

• Add last_used: datetime | None to KeymasterCodeSlot and set it on unlock for valid code slots.
• Create per-slot timestamp sensors (SensorDeviceClass.TIMESTAMP) and include them in Lovelace card generation.
• Expand/adjust tests to cover entity creation, availability, timestamp behavior, and reset behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
custom_components/keymaster/lock.py	Adds last_used field to code slot model and type lookup for (de)serialization.
custom_components/keymaster/coordinator.py	Sets last_used on _lock_unlocked() for the used code slot and triggers coordinator update.
custom_components/keymaster/sensor.py	Creates per-slot last_used sensors using KeymasterSensor + timestamp device class.
custom_components/keymaster/lovelace.py	Inserts “Last Used” entity into slot cards in both regular and parent views.
tests/test_sensor.py	Updates entity counts and adds last-used sensor test coverage.
tests/test_coordinator.py	Adds coordinator tests for setting/clearing last_used and parent behavior.
tests/test_init.py	Updates sensor count assertions to account for the new per-slot sensors.

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[firstof9]

Looks good, interesting idea, did someone request this feature?

[tykeal]

My brain did this morning when I was searching through the logs to see the last time one of my guest rooms in the house had their code used!

[tykeal]

LOL turns out I might have gotten some inspiration from @raman325 as I just noticed that LCM has something like this sensor!

[firstof9]

If you think it's good to merge go for it man.
I assume you've tested it locally on a HA instance right?