[ZhuchkaTriplesix]

Part of #1731 (folders features/redis and features/mongodb, ~175 reads). Epic #1465.

Mechanical, no visual change:

• Theme.of(context).colorScheme and shadcn.Theme.of(context).colorScheme → context.colors;
• the ColorScheme / shadcn.ColorScheme types of parameters and fields → QueryaUiColors. Several widgets took the same scheme twice (colorScheme and shadcnCs); both are QueryaUiColors now, and the colorScheme parameter of the Redis type editors, the key, database and Mongo list rows is named colors;
• tests that build those editors pass colors: from context.colors.

15 files no longer import shadcn: the scheme was all they took from it (Mongo collections, databases, document editor, documents view, explorer, stats; Redis hash, list, set and zset editors, databases, explorer, key editor, keys view, view). They leave the shadcn ratchet: 52 → 37 files.

The guard colors_through_context_test.dart now covers connections, mongodb and redis.

dart analyze is clean; Redis, Mongo, NoSQL, guards, main-screen and e2e suites pass locally.