feat(ai): add pollinations chat, gemini, image endpoints

Ported from Shirokami-API scraper/ai/pollinationsai-{text,gemini,image}.js:
- /ai/chat - OpenAI-compatible chat via text.pollinations.ai (default model 'openai'; source's gpt-5-nano is dead upstream, 404 now triggers fallback)
- /ai/gemini - gemini model via same endpoint
- /ai/image - flux image gen via image.pollinations.ai (returns raw bytes, sniffs JPEG/PNG mime)

Note: pollinations is a free shared API - intermittently 402/502/empty from VPS IP (upstream flakiness, not code)

src/presentation/handler/ai.rs

@@ -0,0 +1,67 @@
+//! Axum handlers for AI endpoints (Pollinations).
+
+use axum::body::Body;
+use axum::extract::Query;
+use axum::http::{header, StatusCode};
+use axum::response::Response;
+use axum::Json;
+use serde::Deserialize;
+use serde_json::Value;
+
+use crate::application::ai as use_cases;
+use crate::presentation::error::AppError;
+
+#[derive(Deserialize)]
+pub struct AiParams {
+    pub text: Option<String>,
+    pub prompt: Option<String>,
+    pub model: Option<String>,
+    pub image_url: Option<String>,
+    pub url: Option<String>,
+    pub width: Option<u32>,
+    pub height: Option<u32>,
+}
+
+/// GET /ai/chat?text=...&prompt=...&model=...
+pub async fn chat_handler(Query(params): Query<AiParams>) -> Result<Json<Value>, AppError> {
+    let text = params
+        .text
+        .ok_or_else(|| AppError::BadRequest("Missing 'text' parameter".to_string()))?;
+    let result = use_cases::chat(text, params.prompt.unwrap_or_default(), params.model).await?;
+    Ok(Json(result))
+}
+
+/// GET /ai/gemini?text=...&prompt=...&image_url=...
+pub async fn gemini_handler(Query(params): Query<AiParams>) -> Result<Json<Value>, AppError> {
+    let text = params
+        .text
+        .ok_or_else(|| AppError::BadRequest("Missing 'text' parameter".to_string()))?;
+    let result =
+        use_cases::gemini(text, params.prompt.unwrap_or_default(), params.image_url).await?;
+    Ok(Json(result))
+}
+
+/// GET /ai/image?prompt=...&model=...&width=...&height=... — returns image bytes.
+pub async fn image_handler(Query(params): Query<AiParams>) -> Result<Response<Body>, AppError> {
+    let prompt = params
+        .prompt
+        .ok_or_else(|| AppError::BadRequest("Missing 'prompt' parameter".to_string()))?;
+    let model = params.model.unwrap_or_else(|| "flux".to_string());
+    let width = params.width.unwrap_or(1024);
+    let height = params.height.unwrap_or(1024);
+
+    let bytes = use_cases::image(prompt, model, width, height).await?;
+    // Pollinations flux returns JPEG by default.
+    let mime = if bytes.starts_with(b"\xff\xd8\xff") {
+        "image/jpeg"
+    } else if bytes.starts_with(b"\x89PNG\r\n\x1a\n") {
+        "image/png"
+    } else {
+        "application/octet-stream"
+    };
+    Ok(Response::builder()
+        .status(StatusCode::OK)
+        .header(header::CONTENT_TYPE, mime)
+        .body(Body::from(bytes))
+        .unwrap())
+}

src/presentation/handler/mod.rs

@@ -1,3 +1,4 @@
+pub mod ai;
 pub mod anime;
 pub mod anime2;
 pub mod downloader;

src/presentation/router.rs

@@ -391,6 +391,19 @@ pub fn build_router(app_state: Arc<AppState>) -> anyhow::Result<Router> {
             "/uploader/file/{name}",
             axum::routing::get(crate::presentation::handler::uploader::serve_file_handler),
         )
+        // AI routes
+        .route(
+            "/ai/chat",
+            axum::routing::get(crate::presentation::handler::ai::chat_handler),
+        )
+        .route(
+            "/ai/gemini",
+            axum::routing::get(crate::presentation::handler::ai::gemini_handler),
+        )
+        .route(
+            "/ai/image",
+            axum::routing::get(crate::presentation::handler::ai::image_handler),
+        )
         // Health
         .route(
             "/health",