Add docs, blog, community pages and polish landing page layout

- Add docs pages (getting-started, changelog, keyboard-shortcuts)
- Add blog, community, and legal pages (privacy, terms, EULA)
- Add site header, footer, download button, and nav components
- Add sitemap and robots.txt generation
- Narrow main page container (max-w-2xl), fix footer positioning
- Switch README feature list to colon style

web/app/docs/docs-nav.tsx

@@ -0,0 +1,137 @@
+"use client";
+
+import { useState, useEffect, useRef, useCallback } from "react";
+import { DocsSidebar } from "../components/docs-sidebar";
+import { DocsPager } from "../components/docs-pager";
+
+export function DocsNav({ children }: { children: React.ReactNode }) {
+  const [open, setOpen] = useState(false);
+  const sidebarRef = useRef<HTMLElement>(null);
+  const buttonRef = useRef<HTMLButtonElement>(null);
+
+  const close = useCallback(() => {
+    setOpen(false);
+    buttonRef.current?.focus();
+  }, []);
+
+  // Close on Escape
+  useEffect(() => {
+    if (!open) return;
+    const handler = (e: KeyboardEvent) => {
+      if (e.key === "Escape") close();
+    };
+    window.addEventListener("keydown", handler);
+    return () => window.removeEventListener("keydown", handler);
+  }, [open, close]);
+
+  // Trap focus inside sidebar when open on mobile
+  useEffect(() => {
+    if (!open || !sidebarRef.current) return;
+
+    const sidebar = sidebarRef.current;
+    const focusable = sidebar.querySelectorAll<HTMLElement>(
+      'a[href], button, [tabindex]:not([tabindex="-1"])'
+    );
+    if (focusable.length === 0) return;
+
+    const first = focusable[0];
+    const last = focusable[focusable.length - 1];
+
+    // Focus first link
+    first.focus();
+
+    const trap = (e: KeyboardEvent) => {
+      if (e.key !== "Tab") return;
+      if (e.shiftKey) {
+        if (document.activeElement === first) {
+          e.preventDefault();
+          last.focus();
+        }
+      } else {
+        if (document.activeElement === last) {
+          e.preventDefault();
+          first.focus();
+        }
+      }
+    };
+
+    sidebar.addEventListener("keydown", trap);
+    return () => sidebar.removeEventListener("keydown", trap);
+  }, [open]);
+
+  // Lock body scroll when open on mobile
+  useEffect(() => {
+    if (!open) return;
+    const mq = window.matchMedia("(min-width: 768px)");
+    if (mq.matches) return; // don't lock on desktop
+    document.body.style.overflow = "hidden";
+    return () => { document.body.style.overflow = ""; };
+  }, [open]);
+
+  return (
+    <div className="max-w-5xl mx-auto flex px-4">
+      {/* Mobile menu button */}
+      <button
+        ref={buttonRef}
+        onClick={() => setOpen(!open)}
+        aria-expanded={open}
+        aria-controls="docs-sidebar"
+        className="fixed bottom-4 right-4 z-40 md:hidden w-10 h-10 rounded-full bg-foreground text-background flex items-center justify-center shadow-lg"
+        aria-label={open ? "Close navigation" : "Open navigation"}
+      >
+        <svg
+          width="16"
+          height="16"
+          viewBox="0 0 24 24"
+          fill="none"
+          stroke="currentColor"
+          strokeWidth="2"
+          strokeLinecap="round"
+          strokeLinejoin="round"
+          aria-hidden="true"
+        >
+          {open ? (
+            <path d="M18 6L6 18M6 6l12 12" />
+          ) : (
+            <>
+              <path d="M3 6h18" />
+              <path d="M3 12h18" />
+              <path d="M3 18h18" />
+            </>
+          )}
+        </svg>
+      </button>
+
+      {/* Mobile overlay */}
+      {open && (
+        <div
+          className="fixed inset-0 z-30 bg-black/50 md:hidden"
+          aria-hidden="true"
+          onClick={close}
+        />
+      )}
+
+      {/* Sidebar */}
+      <aside
+        ref={sidebarRef}
+        id="docs-sidebar"
+        role="navigation"
+        aria-label="Documentation"
+        style={{ height: "calc(100dvh - 3rem)" }}
+        className={`fixed top-12 left-0 z-40 w-56 bg-background py-4 pr-4 overflow-y-auto transition-transform md:sticky md:top-12 md:shrink-0 md:translate-x-0 ${
+          open ? "translate-x-0" : "-translate-x-full"
+        }`}
+      >
+        <DocsSidebar onNavigate={close} />
+      </aside>
+
+      {/* Content */}
+      <main className="flex-1 min-w-0">
+        <div className="max-w-2xl px-6 pb-10 ml-0" data-dev="docs-content" style={{ paddingTop: 8 }}>
+          <div className="docs-content text-[15px]">{children}</div>
+          <DocsPager />
+        </div>
+      </main>
+    </div>
+  );
+}