[P2][SOC-04] Email, calendar, contacts and project actions

Programme: #1
Epic: #28

## Objective
Bring email, calendar, contacts and project systems into the same source-backed workspace/action model so the browser becomes a general work interface, not just a web feed.

## Scope
- Read-first normalized views for messages/threads, contacts, events/calendars and project tasks/items.
- Draft/reply/forward/send actions with exact account, recipients, thread and attachments.
- Calendar create/update/respond with timezone, attendee and conflict checks.
- Contact/source identity preservation and uncertain identity linking.
- Project task/status/comment actions with provider-specific semantics.
- Trusted approvals for consequential sends/meeting changes where policy requires.
- Provider outcome verification and reconciliation.

## Correctness rules
- Exact recipient/account/date/timezone matter; display-name inference is insufficient for writes.
- Draft is distinct from sent; scheduled is distinct from accepted.
- Private sources remain account/workspace scoped throughout normalization/retrieval.

## Acceptance criteria
- [ ] Email send preview/approval identifies exact account, recipients, thread/content and attachments.
- [ ] Calendar writes show timezone, attendees and detected conflicts before commit.
- [ ] External send/update outcome is verified or explicitly unresolved.
- [ ] Private email/calendar/project records cannot leak through cross-account caches/retrieval.
- [ ] Provider-specific task/event semantics remain visible when normalization is incomplete.
- [ ] Read-only workspace remains useful without write permissions.

## Dependencies
- CONN-01
- DATA-01
- TX-01

**First phase:** P2
**Maturity target:** P6
**Owner:** connectors-domains

Start by reviewing the CONN-01, DATA-01, and TX-01 dependencies alongside this issue's scope and correctness rules; no implementation files or tests are identified. Done requires satisfying every acceptance criterion, including verified provider outcomes, exact write previews, conflict checks, and account-scoped records.

Written by the indexing model from the issue text.