Add custom categories feature

- Add support for user-defined custom categories in config.toml
- Update Config struct with categories field and default_categories() function
- Thread categories through GeminiClient and prompt builder
- Update AI prompts to use dynamic categories instead of hardcoded ones
- Add comprehensive documentation with examples for different use cases
- Update tests to support new categories field
- Maintain backward compatibility with default categories
- Update version from 1.0.3 to 1.0.4

Closes feature request for custom categories.

src/main.rs

@@ -3,7 +3,7 @@ use noentropy::cli::{
     Args,
     orchestrator::{handle_organization, handle_undo},
 };
-use noentropy::settings::{get_or_prompt_api_key, get_or_prompt_download_folder};
+use noentropy::settings::{get_or_prompt_config, get_or_prompt_download_folder};
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
@@ -15,10 +15,9 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         return Ok(());
     }
 
-    let api_key = get_or_prompt_api_key()?;
-    let download_path = get_or_prompt_download_folder()?;
+    let config = get_or_prompt_config()?;
 
-    handle_organization(args, api_key, download_path).await?;
+    handle_organization(args, config).await?;
 
     Ok(())
 }