feat: migrate database to PostgreSQL with file-based connection secrets

fix: disable period warnings for payments

feat: improve document attachments and approval exports

feat: streamline document creation forms

feat: improve document access and submission validation

chore: remove frame options middleware header

chore: allow embedding application pages

chore: remove frame ancestors CSP directive

feat: export document summaries to EML

merge: resolve main into security fixes

feat: improve document workflows and UI accessibility

fix: harden authorization and session invalidation

feat: improve document workflows and UI accessibility

feat: show EDO number in role approval cards

fix: load approval queue for role 203

feat: move role 203 setting to users admin

feat: add budgetist letters overview

feat: add document search and role 203 workflow

feat: improve document forms and account controls