feat(infra): add tools service with document scanner, image & PDF tools

Implement self-hosted document scanner and media processing tools as
an alternative to CamScanner/ilovepdf without third-party uploads.

Backend: Rust Axum gateway + worker pool with NATS JetStream queue
Frontend: Next.js 16 + shadcn/ui + Tailwind v4 + Framer Motion
Pipeline: Canny edge detection -> DLT homography warp -> Sauvola
binarization -> Hough deskew -> Tesseract OCR -> searchable PDF

Phase 1 (MVP) delivers:
- Document scanner with perspective correction and OCR
- Image compress/resize/convert tools
- PDF merge/split/compress tools
- Real-time WebSocket progress updates
- Rate limiting, auto-cleanup, Prometheus metrics
- Full CI/CD pipeline with Docker multi-stage build

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

apps/tools/backend/Cargo.toml

@@ -0,0 +1,37 @@
+[workspace]
+resolver = "2"
+
+members = [
+    "common",
+    "gateway",
+    "workers",
+    "wasm",
+]
+
+default-members = [
+    "common",
+    "gateway",
+    "workers",
+]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+
+[workspace.dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+uuid = { version = "1", features = ["v4", "serde"] }
+chrono = { version = "0.4", features = ["serde"] }
+tokio = { version = "1", features = ["full"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["json", "env-filter"] }
+thiserror = "2"
+async-nats = "0.39"
+redis = { version = "0.28", features = ["tokio-comp", "connection-manager", "aio"] }
+image = "0.25"
+imageproc = "0.25"
+lopdf = "0.36"
+reqwest = { version = "0.12", features = ["json"] }
+anyhow = "1"