feat: category assignment in create_task / update_task (v0.4.10)

Verified via FW_DEBUG=1 + systematic param-name probing that the
correct parameter is `taskCategoryId` with value = full metaId from
get_categories (e.g. taskCategory/23431854_200).  Numeric systemCategoryId
alone causes API error; full metaId is accepted and stored.

Changes:
- create_task: add optional category_id parameter → sent as taskCategoryId
- update_task: add optional category_id parameter → sent as taskCategoryId;
  guard now accepts category_id-only updates
- get_tasks: expose category_id field in returned task objects
- get_categories: update docstring (param name now known)
- SPEC.md: document verified taskCategoryId param + clarify categories[]
  vs taskCategoryId field distinction
- scripts/find_category_param.py: discovery script used to find param name

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -23,21 +23,21 @@ eingebunden.
 
 ## Aktueller Stand
 
-### Implementierte Tools (v0.4.8)
+### Implementierte Tools (v0.4.10)
 
 | Kategorie | Tools |
 |---|---|
 | Kreise | `get_circles`, `get_members` |
 | Listen | `get_lists` |
-| Tasks (Lesen) | `get_tasks`, `get_categories` |
+| Tasks (Lesen) | `get_tasks` (inkl. `category_id`), `get_categories` |
 | Wall | `get_activities`, `like_post` |
-| Tasks (Schreiben) | `create_task`, `update_task`, `toggle_task`, `delete_task` |
+| Tasks (Schreiben) | `create_task` (inkl. `category_id`), `update_task` (inkl. `category_id`), `toggle_task`, `delete_task` |
 
 
 ## Roadmap
 
 - v0.x: Erweiterter Lese- + Schreibzugriff ← aktuell
-- Offen: Unlike (`like_post(like=False)`), Task-Kategorie-Zuweisung beim Erstellen/Aktualisieren
+- Offen: Unlike (`like_post(like=False)`)
 
 
 ## Referenzprojekt