refactor: move LLM max input length to global config

The LLM max input length configuration was moved from the session state in app.py to the GlobalConfig class in global_config.py. This change centralizes the configuration and improves maintainability by avoiding hardcoded values in the application logic.

app.py

@@ -172,19 +172,6 @@ with st.sidebar:
         horizontal=True
     )
 
-    # --- LLM Max Input Length Config ---
-    # Only set session state if not already set by user
-    if 'llm_max_input_length' not in st.session_state:
-        st.session_state['llm_max_input_length'] = 400
-    llm_max_input_length = st.sidebar.number_input(
-        'Max LLM Input Length (characters)',
-        min_value=100,
-        max_value=20000,
-        step=100,
-        key='llm_max_input_length',
-        help='Maximum number of characters allowed for the LLM input prompt.'
-    )
-
     if RUN_IN_OFFLINE_MODE:
         llm_provider_to_use = st.text_input(
             label='2: Enter Ollama model name to use (e.g., mistral:v0.2):',
@@ -304,7 +291,7 @@ def set_up_chat_ui():
 
     if prompt := st.chat_input(
         placeholder=APP_TEXT['chat_placeholder'],
-        max_chars=st.session_state.get('llm_max_input_length', 400),
+        max_chars=GlobalConfig.LLM_MODEL_MAX_INPUT_LENGTH,
         accept_file=True,
         file_type=['pdf', ],
     ):

global_config.py

@@ -97,6 +97,7 @@ class GlobalConfig:
     DEFAULT_MODEL_INDEX = int(os.environ.get('DEFAULT_MODEL_INDEX', '4'))
     LLM_MODEL_TEMPERATURE = 0.2
     MAX_PAGE_COUNT = 50
+    LLM_MODEL_MAX_INPUT_LENGTH = 20000  # characters
 
     LOG_LEVEL = 'DEBUG'
     COUNT_TOKENS = False