docs: architecture overview + C4 components + action-result spec sync

New architecture documentation:
- docs/architecture/overview.md: 890-line comprehensive architecture guide
  (system context, patterns, components, data flow, lifecycle, security)
- docs/architecture/c4-components.md: C4 component-level documentation
  (8 components, 3 Mermaid diagrams, component relationships)

action-result.allium spec sync (9 fixes):
- Added allium version header
- Fixed function names (deleteActivityById, startActivityById, etc.)
- Added 14 missing functions (apiKey, notification, module actions)
- Updated automation from "formatError" to "MIGRATED to ActionResult<T>"
- Documented handleError(): ActionResult<never>
- Updated total function count: 117 across 19 files
- Added getJobsIterator as special case (async generator)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rorar