Add project type discovery and activity attachment upload commands

[welias]

What changed

• added a new projects types command to list available project types with their IDs
• added structured output for project type listings in table/json/csv formats
• improved projects create help so --type-id clearly points users to python -m conviso.app projects types
• added a new requirements attach command to upload one or more files to a requirement activity
• extended the GraphQL upload client to support multipart requests with multiple files
• documented both new flows in the README

Why

Creating a project required a type-id, but the CLI did not provide a clear way to discover valid project type IDs. The CLI also lacked a direct way to upload evidences to requirement activities, forcing that workflow outside the tool.

Impact

Users can now discover valid project type IDs directly from the CLI before creating a project, and can upload activity evidences from the CLI with a required reason and one or more files.

Validation

• PYTHONPATH=src ./.venv/bin/python -m py_compile src/conviso/clients/client_graphql.py src/conviso/commands/requirements.py src/conviso/commands/projects.py src/conviso/schemas/projects_schema.py
• PYTHONPATH=src ./.venv/bin/python -m conviso.app projects types --help
• PYTHONPATH=src ./.venv/bin/python -m conviso.app projects create --help
• PYTHONPATH=src ./.venv/bin/python -m conviso.app requirements attach --help
• PYTHONPATH=src ./.venv/bin/python -m conviso.app projects types --limit 3 --format json