Feature/group lupaus agenda items by category

[0is1]

feat(lupaus): group agenda items by category and expose grouped rendering

enrich_related.py:

* Add get_category_from_agenda_item() to extract category (scheme 'categories')
* Add _group_agenda_items_by_category() to build category -> [items] mapping
* Extend (renamed) _set_stt_fields() to attach grouped_items per agenda
* Rename public helper set_stt_fields -> _set_stt_fields (now internal)
* Update enrich_planning_agendas() to call _set_stt_fields() in all paths

lupaus_events_template.html:

* Introduce render_planning_item macro to DRY per-item rendering
* Refactor loop to use agenda.grouped_items and render each category with <h2>
* Preserve existing item formatting (priority, events, coverages)
* Remove previous ungrouped inline rendering code

Result: Templates now support category-based grouping via agenda.grouped_items populated in enrichment.

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feat(lupaus): surface main-topic priorities and show category/main sections

* Add _get_items_with_highest_priority() and attach main_topic_items to each agenda (highest numeric priority = 3300)
* Continue grouping agenda items by category via _group_agenda_items_by_category(), now stored under agenda['grouped_items']
* Template updates:
        * Introduce render_planning_item_category() and render_main_topic_item() helpers
        * Prepend each item line with a dash (“- …”) for bullet-style formatting
        * Render a new “Kärkiaiheitamme” section listing main_topic_items
        * Keep category sections (<h2>{{ category }}</h2>) with existing per-item layout

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feat(lupaus): enrich planning with coverage status and render grouped sections

* enrich_related.py
        * Add _get_planning_item_coverage_status_from_mongo() helper to pull coverages[*].news_coverage_status (limited to g2_content_type == "teksti") from Mongo.
        * During agenda enrichment, attach the retrieved news_coverage_status dict to each planning item before priority filtering.

* lupaus_events_template.html
        * Normalize headings to uppercase (KÄRKIAIHEITAMME, category names).
        * Within each category section, group items by news_coverage_status:
                * “coverage intended” → rendered first with no extra heading.
                * “coverage not decided yet” → rendered under <h2>JOS AIHETTA</h2>.
                * Empty/other statuses → rendered under <h2>EI</h2>.

Result: Lupaus agendas now carry coverage intent metadata and surface it in the template, highlighting intended coverages and separating undecided/other items.

[petrjasek]

merged develop here to fix the tests, fyi we're switching to async version now