Add API usage tracking and dynamic task reloading

Features:
- Usage tracking system (usage_tracker.py)
  - Tracks input/output tokens per API call
  - Calculates costs with support for cache pricing
  - Stores data in usage_data.json (gitignored)
  - Integrated into llm_interface.py

- Dynamic task scheduler reloading
  - Auto-detects YAML changes every 60s
  - No restart needed for new tasks
  - reload_tasks() method for manual refresh

- Example cost tracking scheduled task
  - Daily API usage report
  - Budget tracking ($5/month target)
  - Disabled by default in scheduled_tasks.yaml

Improvements:
- Fixed tool_use/tool_result pair splitting bug (CRITICAL)
- Added thread safety to agent.chat()
- Fixed N+1 query problem in hybrid search
- Optimized database batch queries
- Added conversation history pruning (50 messages max)

Updated .gitignore:
- Exclude user profiles (memory_workspace/users/*.md)
- Exclude usage data (usage_data.json)
- Exclude vector index (vectors.usearch)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

adapters/telegram/adapter.py

@@ -224,12 +224,22 @@ class TelegramAdapter(BaseAdapter):
                     else None
                 )
 
-                sent_message = await self.bot.send_message(
-                    chat_id=chat_id,
-                    text=chunk,
-                    parse_mode=parse_mode,
-                    reply_to_message_id=reply_to_id,
-                )
+                try:
+                    sent_message = await self.bot.send_message(
+                        chat_id=chat_id,
+                        text=chunk,
+                        parse_mode=parse_mode,
+                        reply_to_message_id=reply_to_id,
+                    )
+                except TelegramError:
+                    # Markdown parse errors are common with LLM-generated
+                    # text (unbalanced *, _, etc). Fall back to plain text.
+                    sent_message = await self.bot.send_message(
+                        chat_id=chat_id,
+                        text=chunk,
+                        parse_mode=None,
+                        reply_to_message_id=reply_to_id,
+                    )
 
                 results.append({
                     "message_id": sent_message.message_id,