web: fix OIDC navigation intercepted by the SPA router; tidy table layout

- Login/Logout anchors now carry rel="external": sycamore-router
  intercepts same-origin anchor clicks otherwise, so the OIDC login
  round-trip never left the SPA (found with a real browser test)
- Opponents' hidden hands render as a tidy 5x2 grid of card backs, seats
  have a fixed height and shrink-wrap so the table no longer jumps as
  cards are played
- Dockerfile: cache the Rust target dir so frontend rebuilds are fast
- ignore .playwright-mcp/ tooling output

.gitignore

@@ -10,3 +10,6 @@ build/
 
 # Rust build output
 target/
+
+# Playwright MCP tooling output
+.playwright-mcp/

server/Dockerfile

@@ -34,6 +34,7 @@ COPY web/assets ./assets
 COPY web/src ./src
 
 RUN --mount=type=cache,target=/usr/local/cargo/registry \
+    --mount=type=cache,target=/web/target \
     trunk build --release
 
 # --- Python builder ----------------------------------------------------------

web/src/pages/lobby.rs

@@ -54,7 +54,10 @@ pub fn LobbyPage() -> View {
                 Some(None) => view! {
                     div(class="panel login-panel") {
                         p { "Log in with your account to play." }
-                        a(class="button primary", href="/auth/login") { "Log in" }
+                        // rel="external" opts out of the SPA router's click
+                        // interception: this must be a full page navigation
+                        // to the backend's OIDC login endpoint.
+                        a(class="button primary", href="/auth/login", rel="external") { "Log in" }
                     }
                 },
                 Some(Some(me)) => view! {
@@ -63,7 +66,7 @@ pub fn LobbyPage() -> View {
                             span(class="whoami") { "Signed in as " strong { (me.name.clone()) } }
                             a(href="/history") { "My matches" }
                             a(href="/leaderboard") { "Leaderboard" }
-                            a(href="/auth/logout") { "Log out" }
+                            a(href="/auth/logout", rel="external") { "Log out" }
                         }
                         div(class="panel") {
                             h2 { "New match" }

web/style.css

@@ -252,6 +252,13 @@ table.matches td.lost {
     border-radius: 10px;
     padding: 0.5rem 0.75rem;
     text-align: center;
+    /* Fixed height keeps the table from jumping as cards are played. */
+    display: flex;
+    flex-direction: column;
+    justify-content: flex-start;
+    min-height: 116px;
+    align-self: center;
+    width: 100%;
 }
 
 .seat.active {
@@ -275,9 +282,19 @@ table.matches td.lost {
     color: var(--muted);
 }
 
+/* Opponents' hidden hands: a tidy grid so the count reads at a glance. */
+.seat-cards {
+    display: grid;
+    grid-template-columns: repeat(5, auto);
+    gap: 2px;
+    justify-content: center;
+    margin: 0.35rem 0;
+}
+
 .seat-stats {
     font-size: 0.8rem;
     color: var(--muted);
+    margin-top: auto;
 }
 
 .center {
@@ -287,6 +304,7 @@ table.matches td.lost {
     align-items: center;
     justify-content: center;
     gap: 0.75rem;
+    min-height: 230px;
 }
 
 .table-cards {
@@ -313,7 +331,7 @@ table.matches td.lost {
 }
 
 .card-img.mini {
-    height: 46px;
+    height: 34px;
 }
 
 .card-img.move-card {
@@ -334,6 +352,8 @@ table.matches td.lost {
     flex-wrap: wrap;
     gap: 0.5rem;
     justify-content: center;
+    align-items: flex-end;
+    min-height: 132px;
 }
 
 .hand-slot {