chore: cargo fmt across workspace; add analytics domain to CSP

- Apply cargo fmt to solitaire_engine, solitaire_server formatting.
- solitaire_server/src/lib.rs: add https://analytics.aleshym.co to
  script-src, img-src, and connect-src so the analytics beacon loads
  without a CSP violation.
- docs and README updates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_server/src/lib.rs

@@ -249,11 +249,11 @@ fn build_router_inner(state: AppState, rate_limit: bool) -> Router {
 
 const CSP: &str = concat!(
     "default-src 'self'; ",
-    "script-src 'self' 'unsafe-inline' 'wasm-unsafe-eval'; ",
+    "script-src 'self' 'unsafe-inline' 'wasm-unsafe-eval' https://analytics.aleshym.co; ",
     "style-src 'self' 'unsafe-inline'; ",
     "font-src 'self'; ",
-    "img-src 'self' data:; ",
-    "connect-src 'self'; ",
+    "img-src 'self' data: https://analytics.aleshym.co; ",
+    "connect-src 'self' https://analytics.aleshym.co; ",
     "object-src 'none'; ",
     "frame-ancestors 'none'",
 );