fix(security+audit): strip latent RCE grants, opener allowlist, GDI leaks, CI hardening

From the deep-audit wave (reviewer-verified: capability identifiers valid, no
removed-crate references, GDI free ordering correct):

- Removed 8 never-registered plugins (clipboard-manager, fs, shell, http,
  process, os, dialog, global-shortcut) from Cargo.toml AND their capability
  grants (shell:allow-execute, unscoped fs writes, http:default, …) — verified
  the web never invokes any of them. A latent RCE-class surface is gone.
- on_new_window: only http/https/mailto reach the OS opener (file:///custom
  schemes previously bypassed the opener capability scope entirely).
- set_badge_count: freed hdc + hdc_screen on all three GDI error paths
  (leaked per badge update in a long-running tray app).
- 8s reveal failsafe gated by an AtomicBool: no longer re-shows a window the
  user closed to tray; page-load reveal now fires once only (logout reloads
  don't re-surface a tray-hidden window); recovery for a missed page-load
  event preserved.
- toast.rs: store pruned on Activated too + capped at 20 (was unbounded).
- Startup no longer panics when the bundled icon is missing (tray skipped
  gracefully); msSmartScreenProtection no longer disabled (throttling
  disables kept); rust-version corrected to 1.77.2.
- release.yml update-manifest: fails on empty signatures (was: could publish
  a manifest that traps Windows users in a failed-update loop); partial-
  failure window documented. Deleted the stale upstream tauri.yml workflow.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -2,14 +2,14 @@
 
 [package]
 name = "cinny"
-version = "4.12.2"
+version = "4.12.2" # CI patches src-tauri/tauri.conf.json at build time; that file is the source of truth for the shipped version.
 description = "Yet another matrix client"
 authors = ["Ajay Bura"]
 license = "AGPL-3.0-only"
 repository = "https://github.com/cinnyapp/cinny-desktop"
 default-run = "cinny"
 edition = "2021"
-rust-version = "1.61"
+rust-version = "1.77.2"
 
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
@@ -20,14 +20,7 @@ serde = { version = "1.0.193", features = ["derive"] }
 tauri = { version = "2", features = ["devtools", "wry", "tray-icon", "image-png"] }
 tauri-plugin-localhost = "2"
 tauri-plugin-window-state = "2"
-tauri-plugin-clipboard-manager = "2"
 tauri-plugin-notification = "2"
-tauri-plugin-fs = "2"
-tauri-plugin-shell = "2"
-tauri-plugin-http = "2"
-tauri-plugin-process = "2"
-tauri-plugin-os = "2"
-tauri-plugin-dialog = "2"
 tauri-plugin-opener = "2"
 tauri-plugin-deep-link = "2"
 
@@ -40,7 +33,6 @@ default = [ "custom-protocol" ]
 custom-protocol = [ "tauri/custom-protocol" ]
 
 [target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
-tauri-plugin-global-shortcut = "2"
 tauri-plugin-updater = "2"
 tauri-plugin-single-instance = "2"