fix(dictionary): coerce string boolean values in applyAutoLearnSetting

[hsusul]

Fixes #1921

Problem

In src/helpers/autoLearnSetting.js:

• applyAutoLearnSetting(current, incoming) directly used !!incoming.
• When passed serialized string boolean values (such as "false", "0", or "off") from IPC, query parameters, or stringified storage, Boolean("false") evaluated to true, erroneously turning on auto-learn.

Solution

• Introduced a string-aware boolean coercion helper coerceToBoolean that properly interprets falsey strings ("false", "0", "off", "no", "") and truthy strings ("true", "1", "on", "yes").
• Applied proper coercion to both incoming and current arguments.
• Added unit tests in test/helpers/autoLearnSetting.test.js.

Verification

• node --test test/helpers/autoLearnSetting.test.js (passes, 6/6 tests)
• npm run typecheck (passes, 0 errors)
• npm run lint (passes, 0 errors)
• npm run i18n:check (passes)
• npm run build:renderer (passes)
• git diff --check (clean)