fix(config): drop the __csp_notes field — Tauri config schema is strict

`app.security.__csp_notes` failed `tauri.conf.json` schema validation
("Additional properties are not allowed") on BOTH platforms before any
compile. JSON can't hold comments and Tauri forbids extra keys, so the
rationale lives here instead:

CSP rationale (audit 2026-07): tightened from the fully-open policy.
- 'unsafe-eval' MUST stay: the native→web bridge (forward_deeplink /
  emit_to_web) uses window.eval, governed by page CSP; also covers crypto wasm.
- The sha256 hash allowlists the single inline `window.global ||= window;`
  shim in cinny's index.html (~line 96). If that snippet or its indentation
  changes, recompute the hash or the shim is silently blocked.
- connect-src / img-src / media-src keep http: (plain-http homeservers).
- Review-added: Google Fonts (VT323) + OpenStreetMap iframe (m.location).
- style-src keeps 'unsafe-inline' for React style attributes.

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

src-tauri/tauri.conf.json

@@ -70,7 +70,6 @@
   },
   "app": {
     "security": {
-      "__csp_notes": "Tightened from the fully-open policy (audit 2026-07). script-src: 'unsafe-eval' MUST stay — the native→web bridge (forward_deeplink/emit_to_web) uses window.eval, which page CSP governs (also covers the crypto wasm). The sha256 hash allows the single inline `window.global ||= window;` shim in cinny's index.html (line ~96) — if that snippet or its indentation changes, recompute the hash or the shim is silently blocked. connect-src stays broad: users connect to arbitrary homeservers (img/media keep http: for plain-http homeservers, matching connect-src). Review-added allowances: Google Fonts (VT323 stylesheet+font in index.html) and the OpenStreetMap embed iframe (m.location messages). style-src keeps 'unsafe-inline' for React style attributes.",
       "csp": "default-src 'self'; script-src 'self' 'unsafe-eval' 'sha256-dT6noyex1I8o5CS9Sx/y8UOqwpZYIridpGz92gcObIM='; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' data: https://fonts.gstatic.com; img-src 'self' data: blob: http: https:; media-src 'self' blob: data: mediastream: http: https:; worker-src 'self' blob:; frame-src 'self' blob: https://www.openstreetmap.org; connect-src 'self' blob: data: ipc: ws: wss: http: https: http://ipc.localhost; object-src 'none'; base-uri 'self'"
     }
   }