feat: merge oo-cli and extend library with Calendar/CRM/subtasks/files

- Add Calendar helpers (ListCalendars/ListEvents/AddEvent/DeleteEvent)
- Add CRM helpers: contacts, opportunities, cases, CRM tasks, history notes
- Add project-task extras (ListTasks/ListAllTasks/GetTaskByID/AddTask/
  AddSubtask/UpdateTaskStatus/DeleteTask, GetProjectByID)
- Add UploadOpportunityFile (multipart) and SelfUserID caching
- Introduce Defaults struct, SetDefaults, GetEnvironmentDefaults;
  GetEnvironmentCredentials now accepts ONLYOFFICE_HOST/NAME/PASSWORD aliases
- Add public Authenticate() helper that eagerly primes the token
- Bundle Cobra CLI at cmd/oo-cli with full command surface
  (calendar, tasks, subtasks, CRM, applications-sync); CLI-only deps
  (cobra, godotenv) kept out of the library surface
- Add httptest-based unit tests for form/multipart helpers
- Docs: CHANGELOG, AGENTS, .env.example, README updates for v0.3 features

Consolidates the standalone eSlider/oo-cli tool into this canonical Go
module (see eSlider/inventar ASR-0008).

Made-with: Cursor

CHANGELOG.md

@@ -0,0 +1,47 @@
+# Changelog
+
+All notable changes to this project are documented here. The format is based on
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project
+adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [0.3.0] - 2026-04-24
+
+### Added
+
+- Calendar helpers: `ListCalendars`, `ListEvents`, `AddEvent`, `DeleteEvent`.
+- CRM helpers: contacts (`ListContacts`, `GetContact`, `FindCompany`, `FindPerson`,
+  `CreateCompany`, `CreatePerson`, `AddContactInfo`, `DeleteContact`), deals
+  (`ListOpportunities`, `GetOpportunity`, `CreateOpportunity`,
+  `AddOpportunityMember`, `ListDealStages`, `DeleteOpportunity`), cases
+  (`ListCases`, `CreateCase`, `AddCaseMember`, `DeleteCase`), CRM tasks
+  (`ListCRMTasks`, `CreateCRMTask`, `DeleteCRMTask`, `ListTaskCategories`), and
+  history notes (`AddHistoryNote`).
+- Project task extras: `GetProjectByID`, `ListTasks`, `ListAllTasks`,
+  `GetTaskByID`, `AddTask`, `AddSubtask`, `UpdateTaskStatus`, `DeleteTask`.
+- File upload: `UploadOpportunityFile` (multipart).
+- `SelfUserID` cached lookup of `people/@self`.
+- `Defaults` struct + `SetDefaults` + `GetEnvironmentDefaults` for optional
+  calendar/project fallbacks.
+- Alias env vars accepted by `GetEnvironmentCredentials`:
+  `ONLYOFFICE_HOST` / `ONLYOFFICE_NAME` / `ONLYOFFICE_PASSWORD`.
+- Public `Authenticate()` that primes the token eagerly.
+- Bundled CLI: `cmd/oo-cli` (Cobra) with commands `cal-list`, `cal-events`,
+  `cal-add`, `cal-delete`, `task-list`, `task-add`, `subtask-add`,
+  `task-update`, `crm-contacts`, `crm-add-contact`, `crm-deals`,
+  `crm-add-deal`, `crm-cases`, `applications-sync`.
+- httptest-based unit tests for form / multipart / CRM helpers.
+
+### Changed
+
+- The `onlyoffice.Client` struct gained unexported fields (`defaults`, `selfID`,
+  `noteCatID`); the public API is unchanged and remains backwards compatible.
+
+## [0.2.0] - earlier
+
+- Badges, docs expansion (Gitea sync use case, Gantt/PM workflows).
+
+## [0.1.0] - earlier
+
+- Initial release: OnlyOffice Project Management API client.