feat(api): add model loading, unloading, and uploading endpoints

This commit introduces new API endpoints for managing AI models:
- /models/{model_name}/load: Load a specific model into memory with validation
- /models/{model_name}/unload: Unload a specific model from memory
- /models/upload: Handle model file uploads via multipart form data

The implementation includes proper error handling, model existence validation, and integrates with the existing model manager system. The endpoints return structured JSON responses indicating success or failure states.

The changes also update dependencies to include actix-multipart and futures-util for handling multipart requests, and add path handling utilities for file operations.

src/frontend.rs

@@ -0,0 +1,116 @@
+//! Frontend for ComfyUI-Rust using egui
+
+use eframe::egui;
+
+// Simple UI that connects to our local backend
+pub struct ComfyUiFrontend {
+    prompt: String,
+    negative_prompt: String,
+    width: u32,
+    height: u32,
+    steps: u32,
+    cfg_scale: f32,
+    is_generating: bool,
+    model_name: String,
+}
+
+impl ComfyUiFrontend {
+    pub fn new(_cc: &eframe::CreationContext) -> Self {
+        Self {
+            prompt: "A beautiful sunset over the ocean".to_string(),
+            negative_prompt: "".to_string(),
+            width: 512,
+            height: 512,
+            steps: 30,
+            cfg_scale: 7.0,
+            is_generating: false,
+            model_name: "stable-diffusion-v1-4".to_string(),
+        }
+    }
+
+    fn generate_image(&mut self) {
+        if self.is_generating {
+            return;
+        }
+        
+        self.is_generating = true;
+        let prompt = self.prompt.clone();
+
+        // Simulate async operation by spawning background task that updates UI after delay
+        std::thread::spawn(move || {
+            // Simulate network delay and processing time (5 seconds)
+            std::thread::sleep(std::time::Duration::from_secs(3));
+            
+            println!("Image generation completed for: {}", prompt);
+        });
+    }
+}
+
+impl eframe::App for ComfyUiFrontend {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.heading("ComfyUI-Rust Frontend");
+
+            // Model selection
+            ui.horizontal(|ui| {
+                ui.label("Model:");
+                ui.text_edit_singleline(&mut self.model_name);
+            });
+
+            // Prompt input
+            ui.separator();
+            ui.label("Prompt:");
+            ui.text_edit_multiline(&mut self.prompt);
+
+            ui.label("Negative Prompt:");
+            ui.text_edit_multiline(&mut self.negative_prompt);
+
+            // Generation parameters
+            ui.separator();
+            ui.horizontal(|ui| {
+                ui.label("Width:");
+                ui.add(egui::Slider::new(&mut self.width, 256..=1024).step_by(64.0));
+                
+                ui.label("Height:");
+                ui.add(egui::Slider::new(&mut self.height, 256..=1024).step_by(64.0));
+            });
+
+            ui.horizontal(|ui| {
+                ui.label("Steps:");
+                ui.add(egui::Slider::new(&mut self.steps, 10..=100).step_by(1.0));
+                
+                ui.label("CFG Scale:");
+                ui.add(egui::Slider::new(&mut self.cfg_scale, 1.0..=20.0).step_by(0.5));
+            });
+
+            // Generate button
+            if ui.button("Generate Image").clicked() {
+                self.generate_image();
+            }
+
+            // Status and image preview
+            ui.separator();
+            if self.is_generating {
+                ui.label("Generating image...");
+            } else {
+                ui.label("Ready to generate");
+            }
+        });
+    }
+}
+
+fn main() -> eframe::Result<()> {
+    let options = eframe::NativeOptions {
+        viewport: egui::ViewportBuilder::default()
+            .with_title("ComfyUI-Rust Frontend")
+            .with_inner_size([800.0, 600.0])
+            .with_min_inner_size([400.0, 300.0]),
+        ..Default::default()
+    };
+
+    eframe::run_native(
+        "ComfyUI-Rust",
+        options,
+        Box::new(|cc| Box::new(ComfyUiFrontend::new(cc))),
+    )
+}