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

go.mod

@@ -5,4 +5,10 @@ go 1.22.2
 require (
 	github.com/google/go-querystring v1.2.0
 	github.com/joho/godotenv v1.5.1
+	github.com/spf13/cobra v1.10.2
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.9 // indirect
 )