[TASK][CORE-01.T02] Define typed identities and value objects

Parent: #2

Task ID: `CORE-01.T02`

## Proposed implementation
Implement non-interchangeable ID newtypes and validated resource references. Define money, timestamps, bounded text, content hashes and account-qualified provider IDs with explicit validation.

## Done when
Property tests reject swapped account/task types where possible and malformed monetary, timestamp and size values at runtime.

## Guardrail
IDs must never imply permission; unknown currency scale or source timestamp remains explicitly unknown.

## Prerequisites
`CORE-01.T01`

Review: pending · Implementation: not started.

Start by reading parent issue #2 and completing prerequisite CORE-01.T01; the payload does not identify implementation files or test paths. Use the proposed implementation and guardrail as the scope, then verify that property tests reject swapped identity types and malformed monetary, timestamp, and size values while preserving explicitly unknown currency scales and source timestamps.

Written by the indexing model from the issue text.