Add TypedDict type hints for AirflowPlugin list fields

[sivavarma-x]

Most AirflowPlugin list fields (external_views, react_apps, fastapi_apps, fastapi_root_middlewares, macros) were typed as list[Any], giving plugin authors no static signal about the shape of the entries they're expected to supply.

This PR introduces TypedDict definitions in airflow_shared.plugins_manager that mirror the corresponding API response models (ExternalViewResponse, ReactAppResponse, FastAPIAppResponse, FastAPIRootMiddlewareResponse) and re-exports them from airflow.plugins_manager so plugin authors can annotate their dict literals.

What's typed

• ExternalViewDict — mirrors ExternalViewResponse.
• ReactAppDict — mirrors ReactAppResponse.
• FastAPIAppDict — mirrors FastAPIAppResponse.
• FastAPIRootMiddlewareDict — mirrors FastAPIRootMiddlewareResponse.
• _BaseUIDict factors the common UI fields (name, icon, icon_dark_mode, url_route, category, nav_top_level).
• BaseDestinationLiteral factors the destination values shared between ExternalViewDict and ReactAppDict; ReactAppDict extends it with "dashboard", "dag_overview", "task_overview".
• macros is narrowed from list[Any] to list[Callable[..., Any]].
• _get_ui_plugins() return type is narrowed from tuple[list[Any], list[Any]] to tuple[list[ExternalViewDict], list[ReactAppDict]].

What's left as list[Any]

• flask_blueprints — plugins pass flask.Blueprint instances, not dicts.
• admin_views, menu_links — legacy Flask-Admin.
• appbuilder_views, appbuilder_menu_items — deprecated in the API response in favor of external_views.
• operator_extra_links, global_operator_extra_links, listeners, timetables, windows, partition_mappers, deadline_references, hook_lineage_readers, priority_weight_strategies — class instances, not dict-shaped.

Provider updates

common.ai (HITL Review) and edge3 pick up the new FastAPIAppDict / ReactAppDict types under TYPE_CHECKING guards — no runtime cost.

Backwards compatibility

Runtime behavior is unchanged — TypedDict is a plain dict, so every existing plugin continues to load and render as before. The changes are type-only.
Plugin authors running mypy will now see errors for missing required fields, misspelled keys, or destination values outside the documented set.

closes: #62222

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Was generative AI tooling used to co-author this PR?

• Yes — gpt-5.5 and Claude Opus 4.7

Generated-by: gpt-5.5 and Claude Opus 4.7 following the guidelines

[boring-cyborg]

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