feat: in-app update notice — checks GitHub releases on startup

Adds a one-shot update check that runs on app boot and pops up a small
"Update Available" window when the GitHub releases API reports a newer
tag than this build's `CARGO_PKG_VERSION`.

- `src/update_check.rs` — async wrapper around a blocking `ureq` GET to
  `api.github.com/repos/HakanSeven12/H7CAD/releases/latest`, returns
  `Some(version)` when a newer release exists, `None` otherwise (silent
  on network / parse failure so a missing connection never blocks
  launch).
- `H7CAD::boot` chains a `Task::perform` next to the main-window open
  so the check runs in parallel with first-paint.
- New window plumbed like the other floating panels (page setup, about,
  etc.): `update_notice_window`/`update_notice_version` state, title
  entry, `OsWindowClosed` cleanup, and a `ui::update_notice::view_window`
  modal that shows installed vs. latest version plus "Later" /
  "Open Release Page" buttons. Open routes through `open::that` to the
  releases URL and dismisses the modal.

Dependency: adds `ureq = { version = "2", default-features = false,
features = ["tls"] }` — the smallest blocking HTTP client + TLS combo
that doesn't drag in an async runtime.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.lock

@@ -19,6 +19,7 @@ dependencies = [
  "truck-meshalgo",
  "truck-modeling",
  "truck-polymesh",
+ "ureq",
  "windows-sys 0.59.0",
 ]
 
@@ -4527,6 +4528,20 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "ring"
+version = "0.17.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4689e6c2294d81e88dc6261c768b63bc4fcdb852be6d1352498b114f61383b7"
+dependencies = [
+ "cc",
+ "cfg-if",
+ "getrandom 0.2.17",
+ "libc",
+ "untrusted",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "robust"
 version = "1.2.0"
@@ -4607,6 +4622,41 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.23.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef86cd5876211988985292b91c96a8f2d298df24e75989a43a3c73f2d4d8168b"
+dependencies = [
+ "log",
+ "once_cell",
+ "ring",
+ "rustls-pki-types",
+ "rustls-webpki",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-pki-types"
+version = "1.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30a7197ae7eb376e574fe940d068c30fe0462554a3ddbe4eca7838e049c937a9"
+dependencies = [
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-webpki"
+version = "0.103.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61c429a8649f110dddef65e2a5ad240f747e85f7758a6bccc7e5777bd33f756e"
+dependencies = [
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
@@ -5126,6 +5176,12 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "svg_fmt"
 version = "0.4.5"
@@ -5724,6 +5780,27 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
 
+[[package]]
+name = "untrusted"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"
+
+[[package]]
+name = "ureq"
+version = "2.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "02d1a66277ed75f640d608235660df48c8e3c19f3b4edb6a263315626cc3c01d"
+dependencies = [
+ "base64",
+ "log",
+ "once_cell",
+ "rustls",
+ "rustls-pki-types",
+ "url",
+ "webpki-roots 0.26.11",
+]
+
 [[package]]
 name = "url"
 version = "2.5.8"
@@ -6108,6 +6185,24 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "webpki-roots"
+version = "0.26.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "521bc38abb08001b01866da9f51eb7c5d647a19260e00054a8c7fd5f9e57f7a9"
+dependencies = [
+ "webpki-roots 1.0.7",
+]
+
+[[package]]
+name = "webpki-roots"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52f5ee44c96cf55f1b349600768e3ece3a8f26010c05265ab73f945bb1a2eb9d"
+dependencies = [
+ "rustls-pki-types",
+]
+
 [[package]]
 name = "weezl"
 version = "0.1.12"
@@ -7033,6 +7128,12 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "zeroize"
+version = "1.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+
 [[package]]
 name = "zerotrie"
 version = "0.2.4"