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/tests/fixtures/real/0.51.0.hashes.json

@@ -0,0 +1,10 @@
+{
+ "version": "0.51.0",
+ "raw_len": 993204,
+ "raw_sha256": "a0e86b662cd228497a697d22096e0d888bea40484802a4bf393e5283cc883971",
+ "canonical_len": 756473,
+ "canonical_sha256": "901818050d56e309cedbc5adfbfafa63a30c6d9ac59d85450d9fa0681d1bbc3d",
+ "payload_sha256": "1be8d279322c6d16b7cd7a4e942cfc15207fca795be45bbdbe55f94c42de629f",
+ "release_public_key": "ed25519:DS7z/nhxZE9ffn0PKVtw5fMUBRLdQ424OE236A0tbts=",
+ "app_files": 4950
+}