Fix bugs, N+1 queries, and wire settings in persian-tutor

- Replace inline __import__("datetime").timedelta hack with proper import
- Remove unused import random in anki_export.py
- Add error handling for Claude CLI subprocess failures in ai.py
- Fix hardcoded absolute path in stt.py with relative Path resolution
- Fix N+1 DB queries in vocab.get_flashcard_batch and dashboard.get_category_breakdown
  by adding db.get_all_word_progress() batch query
- Wire Ollama model and Whisper size settings to actually update config
  via ai.set_ollama_model() and stt.set_whisper_size()

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

python/persian-tutor/modules/dashboard.py

@@ -19,17 +19,17 @@ def get_category_breakdown():
     """Return progress per category as list of dicts."""
     vocab = load_vocab()
     categories = get_categories()
+    all_progress = db.get_all_word_progress()
 
     breakdown = []
     for cat in categories:
         cat_words = [e for e in vocab if e["category"] == cat]
-        cat_ids = {e["id"] for e in cat_words}
         total = len(cat_words)
 
         seen = 0
         mastered = 0
-        for wid in cat_ids:
-            progress = db.get_word_progress(wid)
+        for e in cat_words:
+            progress = all_progress.get(e["id"])
             if progress:
                 seen += 1
                 if progress["stability"] and progress["stability"] > 10: