fix(visualization): resolve error handling and edge cases in scenario services

- scenarioIndexedDB: use add() for insert-only, separate updateScenario
- scenarios.service: add try-catch with console.error for DB operations
- scenarios.service: fix "microtask" comment to "macrotask"
- scenarios.service: guard camera access with null check
- scenarios.service: only capture previousResetCamera when patches exist
- applyScenarioDialog: make apply() async and await applyScenario
- getMissingMetrics: filter empty strings in addition to undefined
- uploadFiles.service: add early return for null/empty files
- scenarioApplier: only push metrics patch when overrides exist

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>