fix: remove unused imports and apply ruff formatting

- Remove unused imports: json (llm.py), tempfile (stt.py), base64 (tts.py)
- Apply ruff format to all Python files

theme.py

@@ -3,6 +3,7 @@ Shared Gradio theme for Davies Tech Labs AI demos.
 Consistent styling across all demo applications.
 Cyberpunk aesthetic - dark with yellow/gold accents.
 """
+
 import gradio as gr
 
 
@@ -25,7 +26,12 @@ def get_lab_theme() -> gr.Theme:
         primary_hue=gr.themes.colors.yellow,
         secondary_hue=gr.themes.colors.amber,
         neutral_hue=gr.themes.colors.zinc,
-        font=[gr.themes.GoogleFont("Space Grotesk"), "ui-sans-serif", "system-ui", "sans-serif"],
+        font=[
+            gr.themes.GoogleFont("Space Grotesk"),
+            "ui-sans-serif",
+            "system-ui",
+            "sans-serif",
+        ],
         font_mono=[gr.themes.GoogleFont("JetBrains Mono"), "ui-monospace", "monospace"],
     ).set(
         # Background colors