Restore the imperative settings tab and lower minAppVersion to 1.8.7

Obsidian 1.13 — required by the declarative settings framework adopted
in #307 — remains a Catalyst-only early-access release, which pins
every community-directory user to the 4.1.7 plugin release and makes
the 5.x line unreachable until 1.13 ships publicly. Convert the
settings tab back to the imperative PluginSettingTab.display() API
(reusing the render helpers extracted during the migration) and lower
minAppVersion from 1.13.1 to 1.8.7 so 5.x can reach stable-channel
users now.

The deprecated-API usage (display, setWarning) is intentional;
@typescript-eslint/no-deprecated is downgraded to a warning for plugin
sources until the declarative tab returns. Reverting this commit
restores the declarative settings implementation once Obsidian 1.13
is publicly available.

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