fix(dictation): guard settings and normalize cloudTranscriptionMode in needsSttConfigBeforeStart

[hsusul]

Fixes #1927

Problem

In src/helpers/sttConfigPolicy.js:

• needsSttConfigBeforeStart(settings) used settings || {}, which did not safely guard against non-object primitives.
• s.cloudTranscriptionMode !== "openwhispr" did strict case/whitespace comparisons, causing mixed-casing or whitespace-padded provider strings (e.g., "OpenWhispr" or " openwhispr ") to bypass the config wait and proceed without streaming configuration.

Solution

• Added a proper object check for settings.
• Normalized cloudTranscriptionMode with .trim().toLowerCase().
• Added unit tests in test/helpers/sttConfigPolicy.test.js.

Verification

• node --test test/helpers/sttConfigPolicy.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)