fix: sqlite conn (#1282)

# Summary:
Our tests sometimes error out with
```
========================== 11 passed, 342 warnings in 58.86s ==========================
Error exporting span to SQLite: Cannot operate on a closed database.
Fatal Python error: _enter_buffered_busy: could not acquire lock for <_io.BufferedWriter name='<stdout>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=0x000000012af04280)

Current thread 0x00000001fa29c240 (most recent call first):
  <no Python frame>
```
Usually able to repro this by running 10 times.

The proposed fix is to use threadsafe var for creating sqlite connection
to ensure connection is only used by one thread. Not 100% if this is the
fix, but am not able to repro with this.

# Test Plan:
Run 10 times and saw no more errors
```
for i in {1..10}; do
  echo "=== Starting Run $i ==="
  LLAMA_STACK_CONFIG=fireworks pytest -s -v tests/client-sdk/agents/test_agents.py --safety-shield meta-llama/Llama-Guard-3-8B
  if [[ $? -ne 0 ]]; then
    echo "=== Run $i FAILED with exit code $? ==="
    break
  else
    echo "=== Run $i PASSED ==="
  fi
  echo
done
```

llama_stack/providers/inline/telemetry/meta_reference/sqlite_span_processor.py

@@ -7,6 +7,7 @@
 import json
 import os
 import sqlite3
+import threading
 from datetime import datetime
 
 from opentelemetry.sdk.trace import SpanProcessor
@@ -17,14 +18,18 @@ class SQLiteSpanProcessor(SpanProcessor):
     def __init__(self, conn_string):
         """Initialize the SQLite span processor with a connection string."""
         self.conn_string = conn_string
-        self.conn = None
+        self._local = threading.local()  # Thread-local storage for connections
         self.setup_database()
 
-    def _get_connection(self) -> sqlite3.Connection:
-        """Get the database connection."""
-        if self.conn is None:
-            self.conn = sqlite3.connect(self.conn_string, check_same_thread=False)
-        return self.conn
+    def _get_connection(self):
+        """Get a thread-local database connection."""
+        if not hasattr(self._local, "conn"):
+            try:
+                self._local.conn = sqlite3.connect(self.conn_string)
+            except Exception as e:
+                print(f"Error connecting to SQLite database: {e}")
+                raise e
+        return self._local.conn
 
     def setup_database(self):
         """Create the necessary tables if they don't exist."""
@@ -168,9 +173,14 @@ class SQLiteSpanProcessor(SpanProcessor):
 
     def shutdown(self):
         """Cleanup any resources."""
-        if self.conn:
-            self.conn.close()
-            self.conn = None
+        # We can't access other threads' connections, so we just close our own
+        if hasattr(self._local, "conn"):
+            try:
+                self._local.conn.close()
+            except Exception as e:
+                print(f"Error closing SQLite connection: {e}")
+            finally:
+                del self._local.conn
 
     def force_flush(self, timeout_millis=30000):
         """Force export of spans."""