fix(db): drop sqlite3_flutter_libs to stop SQLCipher symbol-clash segfault

drift_flutter pulled sqlite3_flutter_libs, whose bundled plain SQLite exports
the same sqlite3_* symbols as sqlcipher_flutter_libs. With both loaded the app
segfaulted at startup on Linux desktop when opening the encrypted DB (the app
built and the Dart VM started, then crashed natively — "Lost connection").

drift_flutter was unused (we open the DB via our own encrypted executor), so
removing it drops sqlite3_flutter_libs and leaves SQLCipher as the only native
sqlite provider. 37 tests green; Linux build runs without crashing.

pubspec.lock

@@ -225,14 +225,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.31.0"
-  drift_flutter:
-    dependency: transitive
-    description:
-      name: drift_flutter
-      sha256: c07120854742a0cae2f7501a0da02493addde550db6641d284983c08762e60a7
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.2.8"
   equatable:
     dependency: transitive
     description:
@@ -953,14 +945,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.9.4"
-  sqlite3_flutter_libs:
-    dependency: transitive
-    description:
-      name: sqlite3_flutter_libs
-      sha256: eeb9e3a45207649076b808f8a5a74d68770d0b7f26ccef6d5f43106eee5375ad
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.5.42"
   sqlparser:
     dependency: transitive
     description: