ODIAN Launcher: hub, installer, local stack and remembered sign-in (M2)

- Tauri 2 + Svelte 5 hub in ODIAN dark: patch notes and roadmap, install and
  update progress, local stack status, settings with DHP and MCP addresses.
- crates/odian-packs: Rust installer for pack format v1 (signed manifests,
  resumable verified downloads from a DHP or an ODIAN drive), byte-compatible
  with ODIAN_MCP_Server's Python odian_packs.
- Local stack on 127.0.0.1: Postgres -> Engine API -> tile server -> Odian.exe,
  one Job Object, clean shutdown; database snapshot restore on a fresh PC only.
- Keycloak sign-in through the DHP's MCP, remembered until Sign out with a
  launcher session that renews the Engine token silently.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/odian-packs/src/lib.rs

@@ -0,0 +1,73 @@
+//! ODIAN packs, format v1: verify a signed version manifest and install that version from a
+//! site's update service or from an ODIAN drive, checking every byte.
+//!
+//! A byte-for-byte compatible port of the Python installer (`odian_packs.fetch` in
+//! ODIAN_MCP_Server; the format is its `src/odian_packs/README.md`). An install made by
+//! either one is resumed and re-verified by the other: same layout, same progress files.
+//!
+//! ```text
+//! dest/versions/<v>/manifest.json         written LAST: its presence means "installed"
+//! dest/versions/<v>/<app paths>
+//! dest/data/db/<snapshot>/...
+//! dest/data/src/<paths>                   + <path>.chunks.json while partial, <path>.ok when done
+//! dest/data/tiles/<style>/<dataset>/<z>/<x>/<y><ext>   + .blocks-done.json
+//! ```
+
+pub mod canonical;
+pub mod error;
+pub mod hashing;
+pub mod manifest;
+pub mod signing;
+pub mod tiles;
+
+mod copy;
+mod install;
+mod progress;
+mod source;
+mod tileblocks;
+
+pub use canonical::canonical_bytes;
+pub use error::{Error, IntegrityKind, Result};
+pub use install::{
+    install, AppSummary, DbSummary, InstallOptions, SrcFileSummary, Summary, TileSetSummary,
+};
+pub use manifest::{safe_relpath, validate, Manifest, VerifiedManifest};
+pub use progress::{Progress, Stage};
+pub use source::Source;
+
+use tokio_util::sync::CancellationToken;
+
+/// The ODIAN release public key that ships with the launcher (`ed25519:<base64>`).
+pub fn bundled_public_key() -> &'static str {
+    include_str!("../keys/odian-release.pub").trim()
+}
+
+/// The source's CURRENT version manifest: fetched, validated and signature-checked.
+/// The raw bytes are kept ([`VerifiedManifest::raw`]) because the install writes them verbatim.
+pub async fn current_manifest(source: &Source, public_key: &str) -> Result<VerifiedManifest> {
+    let backend = source::Backend::new(source)?;
+    let raw = backend.current_manifest(&CancellationToken::new()).await?;
+    VerifiedManifest::from_bytes(raw, public_key)
+}
+
+/// A specific version's manifest, verified, and checked to really be that version.
+pub async fn version_manifest(source: &Source, version: &str, public_key: &str) -> Result<VerifiedManifest> {
+    let backend = source::Backend::new(source)?;
+    let raw = backend.version_manifest(version, &CancellationToken::new()).await?;
+    let verified = VerifiedManifest::from_bytes(raw, public_key)?;
+    if verified.version() != version {
+        return Err(Error::integrity(
+            IntegrityKind::Version,
+            format!("manifest for {version}"),
+            format!("asked for {version}, the signed manifest says {}", verified.version()),
+        ));
+    }
+    Ok(verified)
+}
+
+/// A version's patch notes (Markdown). **Untrusted text**: not covered by the signature.
+pub async fn fetch_notes(source: &Source, version: &str) -> Result<String> {
+    let backend = source::Backend::new(source)?;
+    let raw = backend.notes(version, &CancellationToken::new()).await?;
+    Ok(String::from_utf8_lossy(&raw).into_owned())
+}