feat(mail): add recipient address column

[keilogic]

Summary

• add a persisted Recipient column view option to the message-list view menu
• show recipient email addresses in regular incoming-folder lists from parsed message To/Cc data
• show recipient email addresses in indexed search results from indexed recipient data, while avoiding a duplicate column for plain Sent-folder views
• keep wrapped-row behavior anchored to the Subject column when the optional column is inserted

Tests

• npm ci
• npx tsc -p src/tsconfig.app.json --noEmit
• npx tsc -p src/tsconfig.spec.json --noEmit
• npx ng test runbox7 --watch=false --browsers=FirefoxHeadless --include src/app/common/messagelist.spec.ts --include src/app/xapian/searchmessagedisplay.spec.ts
• npx eslint src/app/app.component.ts src/app/app.component.html src/app/common/messagelist.ts src/app/common/messagelist.spec.ts src/app/xapian/searchmessagedisplay.ts src/app/xapian/searchmessagedisplay.spec.ts
• npm run lint -- --quiet
• npx ng test runbox7 --watch=false --browsers=FirefoxHeadless
• npm run policy
• node src/build/pre-build.js
• npx ng build --configuration production --base-href=/app/ runbox7
• node src/build/post-build.js

AI Disclosure

This contribution was developed with assistance from OpenAI Codex. Codex helped inspect the current Runbox 7 source, draft the implementation, add the focused specs, and run the validation commands listed above.

Closes #754