[Enhancement] Support optional time-to-live expiry on individual clipboard entries [Reopen: #32]

[shaaravraghu]

NEW CONTRIBUTORS FIRST PREFERENCE.

Description
Certain clipboard entries such as passwords, tokens, or temporary codes should not persist indefinitely. An optional TTL should be configurable per entry or globally so that sensitive content is automatically removed from the ring and disk after a defined duration without requiring manual deletion.

Steps to Reproduce

1. Copy sensitive content such as a password or API token.
2. Leave the system idle for an extended period.
3. Observe that the sensitive entry remains in the ring indefinitely.

Expected Behavior
When a TTL is set — either globally in config or per entry — the entry should be automatically deleted from the ring, disk, and vault once the TTL has elapsed, with no user intervention required.

Actual Behavior
Entries persist indefinitely regardless of their content or sensitivity. No automatic expiry mechanism exists.

Example
A user copies a one-time login code. An hour later the code has expired externally but still sits in the ring, creating an unnecessary record of a sensitive value.

Suggested Fix
Store a creation timestamp and optional TTL value with each entry. Introduce a background task that periodically scans the ring and removes any entries whose creation time plus TTL is in the past. Apply the same check on load from disk.

[Suji2007hub]

Assign me

[shaaravraghu]

Please let me know how do you plan to implement this?

[Suji2007hub]

1. I would integrate this by extending the clipboard entry model to include metadata fields such as created_at and an optional ttl. When a new entry is added, the current timestamp is stored along with either the entry-specific TTL or a default global TTL from configuration.
2. A background cleanup routine would periodically scan the clipboard ring and identify expired entries by comparing created_at + ttl against the current time. Expired entries would be removed from memory, deleted from disk persistence, and removed from the vault if applicable.
3. To handle cases where the application is restarted, the same expiration check would also run during startup when entries are loaded from disk. Any entries that have already exceeded their TTL would be discarded immediately.
4. The implementation would be designed so that entries without a configured TTL continue to behave as they do today, ensuring backward compatibility while allowing users to enable automatic expiry for sensitive clipboard content.