feat(api): add obscura-api crate with Browser + Page + Element + CookieStore (#191)

* feat(api): add obscura-api crate with Browser + Page API

Adds a Rust library crate exposing Obscura as a programmable browser:
- Browser: build with config (proxy, stealth, UA, storage_dir)
- Page: goto, url, evaluate, content
- BrowserBuilder with fluent API
- examples/basic.rs

Part of #169

* feat(api): add Element API + CookieStore + wait_for_selector

- Element: text(), attribute(), click() via JS evaluation
- CookieStore: set/get_all/get_for_url/save_to_file/load_from_file
- Page::wait_for_selector with 100ms polling
- Page::query_selector for single element lookup
- Updated examples/basic.rs with full interaction demo

Part of #169

* feat(api): add Browser::cookies() method

* refactor(api): move to obscura crate with feature flag

- Renamed obscura-api → obscura (per maintainer feedback #169)
- API enabled by default via 'api' feature flag
- Usage: cargo add obscura (default=api) or cargo add obscura --features api
- Removed separate obscura-api crate

* chore: exclude docker workflow from fork

* fix(api): make the obscura crate build, run, and document install correctly

- examples/basic.rs and the lib.rs doctest imported `obscura_api`, but the crate
  is named `obscura`, so both failed to compile. Use the real crate name.
- wait_for_selector / query_selector read the node id with `Value::as_u64`, but
  `evaluate` returns JS numbers as f64, so it was always None and every
  wait_for_selector timed out. Accept an integer or a non-negative finite float.
- restore .github/workflows/docker.yml, which the PR removed (a fork-specific
  change that should not land upstream).
- add crates/obscura/README.md with honest install instructions: the crate is not
  on crates.io, so depend on it via git (and it builds the embedded V8 from
  source). The `cargo add obscura` form does not work yet.

Verified: workspace + example build, the lib doctest passes, the example runs end
to end (goto, wait_for_selector, text, attribute), and the integration suite is
28/28 with no regressions.

---------

Co-authored-by: zhangyang-crazy-one <[email protected]>
Co-authored-by: SGavrl <[email protected]>

crates/obscura/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "obscura"
+version = "0.1.0"
+edition = "2021"
+description = "Rust API for the Obscura headless browser"
+readme = "README.md"
+repository = "https://github.com/h4ckf0r0day/obscura"
+license = "Apache-2.0"
+
+[features]
+default = ["api"]
+api = ["obscura-browser", "obscura-net", "tokio"]
+
+[dependencies]
+obscura-browser = { path = "../obscura-browser", optional = true }
+obscura-net = { path = "../obscura-net", optional = true }
+anyhow = "1"
+tokio = { version = "1", features = ["rt"], optional = true }
+thiserror = "1"
+serde_json = "1"
+serde = { version = "1", features = ["derive"] }
+url = "2"