fix(tools): resolve external MySQL/PG client tools correctly (#44)

Addresses #44 (closed after the v0.8.3 release builds are green).

Three independent defects in one shared tool-resolution path: bundled tools were
looked up at the wrong path (so bundled fallback never worked, for PostgreSQL
too), macOS GUI apps inherit launchd's minimal PATH, and only mariadb-dump/mariadb
were probed — never mysqldump/mysql, which is what brew install mysql-client
installs. Both engines now resolve through one headless, cached, timed resolver,
plus a non-blocking client/server version warning.

Also fixes passing MySQL-only CLI options to the bundled MariaDB client, and
carries the tool-page UI polish and the requested #40 icon revert.

package.json

@@ -8,8 +8,6 @@
     "tauri:dev": "bun run --filter gridline-desktop tauri:dev",
     "dev:www": "bun run --filter gridline-www dev",
     "build:www": "bun run --filter gridline-www build",
-    "test": "bun run --filter gridline-desktop test",
-    "icons": "bash scripts/regenerate-icons.sh",
-    "icons:verify": "bun scripts/verify-app-icon.mjs"
+    "test": "bun run --filter gridline-desktop test"
   }
 }