…te values (dfinity#3770)

Certified attribute values were encoded as raw bytes (`Blob`) regardless
of their semantic type. This changes the ICRC-3 attribute message to use
the correct types: `Text` for string values (email, name), `Blob` for
binary data (nonce), and `Nat` for timestamps.

# Changes

- `prepare_icrc3_attributes` now produces `Icrc3Value::Text` for
attribute values, `Icrc3Value::Blob` for nonce, and `Icrc3Value::Nat`
for timestamps instead of encoding everything as `Blob`.
- `icrc3_attribute_message` accepts `BTreeMap<String, Icrc3Value>`
instead of `BTreeMap<String, Vec<u8>>`.
- E2e tests updated to verify correct ICRC-3 Value types in the decoded
attribute map.

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Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

…architecture (dfinity#3777)

The authorize flow previously had request handling intertwined with UI
components — handlers would trigger UI changes directly, and UI
components would drive handler logic. This made the flow hard to follow
and brittle to change.

This PR introduces a clean separation: **handlers ← stores → UI**.
Channel handlers write to stores and observe stores (via
`waitForStore`). The UI reads stores to decide what to render, and
writes to stores when the user takes action. Neither side knows about
the other.

# Changes

- **Extract channel handlers into dedicated files.**
`channelHandlers/icrc25.ts` (standards, permissions),
`channelHandlers/delegation.ts` (ICRC-34), and
`channelHandlers/attributes.ts` (legacy + ICRC-3 attributes) — each
self-contained with their own imports.
- **Split authorization store into context and outcome.**
`authorizationStore` holds the request context (`effectiveOrigin`),
`authorizedStore` holds the outcome (`accountNumber`). Handlers
`waitForStore(authorizedStore)` instead of polling a combined state.
- **Add `waitForStore` utility.** Generic helper that resolves when a
Svelte store value satisfies a condition — eliminates repeated
subscribe/unsubscribe boilerplate across handlers.
- **Gate attribute handlers on dapp opt-in.** Attributes are only served
to known dapps with `certifiedAttributes: true`, or in dev environments
(`fetch_root_key`). Unknown origins get an error response.
- **Channel error component.** Extracted `ChannelError.svelte` with
per-error-type messages, shared across channel, pending-channel, and
resuming-channel layouts.
- **Fix pending/resuming channel layout guards.** Pending-channel now
renders errors. Resuming-channel waits for channel establishment before
rendering children, shows errors when appropriate.
- **Remove `AuthorizationChannel.svelte`.** Layouts call
`channelStore.establish()` directly and gate rendering on store state.

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