feat(web): switch to the Alpine CSP build; drop 'unsafe-eval' from CSP

Standard Alpine evaluates every attribute expression through
new Function(), which a strict Content-Security-Policy cannot allow.
Swap to the official CSP-safe build (@alpinejs/csp), whose parser
evaluates expressions against registered component scope without
eval. script-src now carries only 'self' and 'unsafe-inline' (the
latter still required by the pre-paint theme flash guard).

Bindings rewritten out of the unsupported expression shapes:
- 21 multi-statement sequences across admin, audio_reader, docs,
  header, index, and reader became single component methods
  (init/loadWatchStatus hooks, commitScrub, pickSkip, pickSpeed,
  pickDefaultSpeed, chooseSleepOption, chooseSleepClockMode,
  toggleFxInvert, openPageThumbs, submitNote, clearSearch,
  pickReadingTheme)
- the header sidebar's inline x-data (openPanel/themeMode IIFE)
  became a registered sidebarShell component; openPanel itself moved
  to the header root so every sidebar panel shares one open state
- the appearance-panel  moved into the component init()
- header init() now also seeds openPanel from localStorage (or the
  admin section on /admin pages)

Alpine magics (, , , ) remain available —
the CSP evaluator injects them into scope.

The Playwright suite covers the converted surfaces end to end.

web/src/header.ts

@@ -121,7 +121,60 @@ const initializeScanListener = function (this: any) {
 export { logout, restoreLibrarySelection };
 
 Alpine.data("header", () => ({
+  init() {
+    // Shared panel state: one open panel across all sidebar panels. Default
+    // to the persisted panel (or the admin section on /admin pages).
+    try {
+      const v = localStorage.getItem("sidebar-open-panel");
+      this.openPanel =
+        v !== null
+          ? v === ""
+            ? null
+            : v
+          : window.location.pathname.startsWith("/admin")
+            ? "admin"
+            : null;
+    } catch {
+      this.openPanel = window.location.pathname.startsWith("/admin") ? "admin" : null;
+    }
+    initializeSearch();
+    this.initializeTheme();
+    this.loadWoodPaneling();
+    this.updateWoodPanelingIndicators();
+    this.restoreLibrarySelection();
+    this.initializeScanListener();
+    // Persist the sidebar's open panel across navigations (was an inline
+    // x-init $watch on the panel element).
+    this.$watch("openPanel", (v: unknown) => {
+      try {
+        localStorage.setItem("sidebar-open-panel", v === null ? "" : String(v));
+      } catch {
+        /* private-mode localStorage failures are non-fatal */
+      }
+    });
+  },
+  openPanel: null as string | null,
+  // Shadow copy for the root-level toggleAppearancePanel: the sidebar shell's
+  // own themeMode (initialized from the server) is the one that matters at
+  // runtime — the merged Alpine scope reads the nearest declaration.
+  themeMode: "",
   mobileMenuOpen: false,
+  // Shared panel toggles: invoked from the sidebar shell's scope, so `this`
+  // is the merged data stack (shell themeMode + root openPanel).
+  toggleAppearancePanel() {
+    this.openPanel = this.openPanel === "appearance" ? null : "appearance";
+    if (this.openPanel === "appearance") {
+      this.$nextTick(() => this.revealCurrentTheme(this.themeMode));
+    }
+  },
+  setThemeMode(mode: string) {
+    this.themeMode = mode;
+    this.$nextTick(() => this.revealCurrentTheme(mode));
+  },
+  selectTheme(name: string) {
+    changeTheme(name);
+    this.openPanel = null;
+  },
   logout,
   initializeSearch,
   initializeTheme,
@@ -137,3 +190,25 @@ Alpine.data("header", () => ({
   scanNewItems: 0,
   scanFilesScanned: 0,
 }));
+
+// Sidebar shell: owns the appearance panel's theme-mode state. The shared
+// openPanel lives on the header root (one open panel across all panels).
+// Registered (not inline x-data) so its methods work under the CSP-safe
+// Alpine build, which cannot evaluate arbitrary inline sentences.
+Alpine.data("sidebarShell", (initialThemeMode: string) => ({
+  themeMode: initialThemeMode,
+  toggleAppearancePanel() {
+    this.openPanel = this.openPanel === "appearance" ? null : "appearance";
+    if (this.openPanel === "appearance") {
+      this.$nextTick(() => this.revealCurrentTheme(this.themeMode));
+    }
+  },
+  setThemeMode(mode: string) {
+    this.themeMode = mode;
+    this.$nextTick(() => this.revealCurrentTheme(mode));
+  },
+  selectTheme(name: string) {
+    changeTheme(name);
+    this.openPanel = null;
+  },
+}));