feat: render HTML email bodies via flutter_html

Email detail screen now renders the message htmlBody with the flutter_html
widget when present, falling back to SelectableText for plain-text-only mail.
Remote http(s) images are blocked by default to defeat tracking pixels; an
opt-in "Load remote images" button reveals them per-screen.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

next.md

@@ -17,49 +17,3 @@ Git repo should not contain unknown files.
 Then commit.
 
 ## Tasks
-
-### Render HTML email bodies
-
-#### Current state
-
-HTML mail *reading* (transport + storage) is already implemented: the IMAP
-fetcher stores the HTML body on `EmailBody.htmlBody`
-(`lib/core/models/email.dart:89`). What is missing is HTML *rendering*:
-`lib/ui/screens/email_detail_screen.dart:158` currently strips tags via
-`htmlToPlain(body.htmlBody ?? '')` and shows the result as plain text.
-
-#### Plan
-
-1. Add `flutter_html: ^3.0.0` to `pubspec.yaml`.
-   - Mature, pure-Dart (no JS / no platform views), works on desktop +
-     mobile + web.
-2. Update `lib/ui/screens/email_detail_screen.dart` `_buildBody`:
-   - Prefer `body.htmlBody` over `body.textBody`.
-   - If `htmlBody` is present and non-empty, render with the `Html` widget.
-   - Else fall back to the current `SelectableText(textBody)` path.
-3. Block remote image loading by default (privacy — defeats tracking
-   pixels). At the top of an HTML message, show a small
-   "Load remote images" button that flips a per-screen `bool` and
-   re-renders. Implement by passing a custom image-loading delegate to
-   `flutter_html` that returns an empty widget for `http(s)` images
-   until the flag is set. Inline `cid:` images are out of scope for
-   this task.
-4. Leave `htmlToPlain` in place — it is still used for reply / forward
-   quoting (`_quotedBody`) where plain text is correct.
-5. No DB schema changes, no generated-code changes, no migration.
-6. No new tests required (pure UI rendering change). Existing widget /
-   integration tests must keep passing.
-
-#### Out of scope (follow-ups if needed)
-
-- Clickable / launchable links inside HTML.
-- Dark-mode HTML colour normalisation.
-- Sandboxed rendering via `WebView` / `flutter_inappwebview`.
-- Inline `cid:` image resolution.
-
-#### Verification
-
-- `task deploy-android` succeeds.
-- Manual: open an HTML newsletter — formatting (lists, bold, links) is
-  visible instead of raw tags or stripped text.
-- Manual: a plain-text-only email still renders unchanged.