fix(#187): Implement 'Other' option for dropdowns, multiple choice & checkboxes

[Absy00]

Summary

Resolves #187 — When "Other" is enabled for dropdown/multiple choice/checkbox questions, an input field now appears for the respondent to type a custom answer. The answer is submitted as { other: "custom value" } and the backend correctly extracts and uses the custom value for RAG analytics.

Changes

Frontend

• QuestionEditor.tsx — Added "Allow Other" checkbox for dropdown, multiple choice, and checkbox question types
• PublicFormView.tsx — Shows text input when "Other" is selected; submits as { other: "..." }
• FormPreview.tsx — Same "Other" input logic in preview mode
• RawResponsesTable.tsx — Fixed [object Object] display bug; now shows Other: custom value

Backend

• form.schema.ts — Added canBeOther: boolean to Question schema
• response.service.ts — Normalizes { other } answers with metadata.normalizedValue; handles "Other" in analytics grouping
• prompt.builder.ts — Extracts .other value for RAG/LLM prompts (language-independent)
• response.processor.ts — Robust text content detection that handles old responses without hasTextContent metadata

Test data & docs

• generate-fake-responses.ts — Generates { other: "..." } test data for all question types with canBeOther
• architecture_overview.md — Documents the "Other" value data structure

Acceptance Criteria (all met)

• Frontend: Input appears when "Other" is selected
• Frontend: Submits as { other: "..." } (not just the label)
• Backend: Prompt builder extracts .other value for analytics
• Multilingual: Logic is label-independent
• Schema: canBeOther property documented

Known issue (separate from #187)

The analytics pipeline (BullMQ worker) experiences job stalling under the default lock settings. This is an infrastructure concern tracked separately — the lockDuration and stalledInterval need to be increased for long-running AI analysis jobs. The "Other" value handling itself works correctly end-to-end.

[rkorszun]

Btw some '' vs "" formatiing in some cases is strange but overall is ok