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/app.py

@@ -7,6 +7,7 @@ import time
 
 import gradio as gr
 
+import ai
 import db
 from modules import vocab, dashboard, essay, tutor, idioms
 from modules.essay import GCSE_THEMES
@@ -214,6 +215,15 @@ def do_anki_export(cats_selected):
     return path
 
 
+def update_ollama_model(model):
+    ai.set_ollama_model(model)
+
+
+def update_whisper_size(size):
+    from stt import set_whisper_size
+    set_whisper_size(size)
+
+
 def reset_progress():
     conn = db.get_connection()
     conn.execute("DELETE FROM word_progress")
@@ -491,6 +501,10 @@ with gr.Blocks(title="Persian Language Tutor") as app:
 
             export_btn.click(fn=do_anki_export, inputs=[export_cats], outputs=[export_file])
 
+            # Wire model settings
+            ollama_model.change(fn=update_ollama_model, inputs=[ollama_model])
+            whisper_size.change(fn=update_whisper_size, inputs=[whisper_size])
+
             gr.Markdown("### Reset")
             reset_btn = gr.Button("Reset All Progress", variant="stop")
             reset_status = gr.Markdown("")