test: full test coverage — 82 tests across all modules, zero warnings
Added tests for 3 uncovered modules:
- db: open, migrate, idempotent migration, FK/WAL pragmas, clone shares conn
- theme: seed_builtins (7 themes), idempotent seed, get_by_name, hex color
validation, sort ordering, case sensitivity
- rdp/input: scancode lookup, extended key detection, value extraction,
mouse flag composition, map coverage assertion
Existing test count: 52 (vault, connections, credentials, settings, host_keys)
New tests added: 30
Total: 82 tests, all passing, zero compiler warnings
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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