chore: rebrand package metadata, pin engines and drop tooling cache

- package.json: homepage/repository point at this repository, node >=22 declared, @mariozechner/pi-coding-agent added as devDependency (extensions/piagentui-server.ts imports it)
- Cargo.toml: repository field filled
- .pi-lens/ ignored and its cached review graph removed from tracking
- three material icons replaced by their 32x32 sources (the committed 16x16 files were broken)

src-tauri/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.6.10"
 description = "Pi Agent UI - Tauri Desktop & Mobile App"
 authors = ["lehhair"]
 license = "GPL-3.0-only"
-repository = ""
+repository = "https://github.com/evandrodevbr/PiAgentUI"
 edition = "2021"
 rust-version = "1.85.0"