feat: initial tools service with document scanner, image & PDF tools

Self-hosted document scanner and media processing tools.
- Rust Axum gateway + worker pool with NATS JetStream
- Next.js 16 frontend with shadcn/ui
- Scanner pipeline: edge detection, warp, binarization, OCR
- Image tools: compress, resize, convert
- PDF tools: merge, split, compress
- CI/CD with Docker multi-stage build

Co-Authored-By: Kilo <kilo@kilo.ai>

backend/wasm/src/lib.rs

@@ -0,0 +1,18 @@
+use wasm_bindgen::prelude::*;
+
+/// Placeholder for WASM image processing.
+/// Full implementation in Phase 2.2.
+#[wasm_bindgen]
+pub fn greet() -> String {
+    "tools-wasm: ready".to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_greet() {
+        assert_eq!(greet(), "tools-wasm: ready");
+    }
+}