Gas floor fix, chain guard, and dashboard footer

- wallet.js: fetch correct EIP-1559 fees from the network (Amoy/Polygon Bor
  enforce a ~25-30 gwei priority floor MetaMask's estimate misses) via new
  /api/gas; hard chain-guard before signing so a tx never lands on the wrong
  network; accept the wallet's usual networks in AppKit so its modal stops
  looping and drive add+switch ourselves.
- chain.js: suggestedFees() from eth_maxPriorityFeePerGas + base fee.
- Dashboard: move the Site links (Ad packages / Live ledger / The contract)
  out of the sidebar into a page footer; hide the sidebar scrollbar.

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

public/assets/site.css

@@ -227,7 +227,7 @@ textarea{resize:vertical;font:inherit}
 /* ── member back-office shell ─────────────────────────── */
 .bo-body{background:var(--ground)}
 .bo{display:grid;grid-template-columns:236px 1fr;min-height:100vh}
-.bo-side{position:sticky;top:0;height:100vh;overflow-y:auto;display:flex;flex-direction:column;gap:22px;
+.bo-side{position:sticky;top:0;height:100vh;overflow-y:auto;scrollbar-width:none;-ms-overflow-style:none;display:flex;flex-direction:column;gap:22px;
   padding:22px 16px;background:rgba(10,18,15,.92);border-right:1px solid var(--line)}
 .bo-side .logo{font-size:19px;padding:0 8px}
 .bo-menu{display:flex;flex-direction:column;gap:4px}
@@ -243,6 +243,10 @@ textarea{resize:vertical;font:inherit}
 .bo-links a:hover{color:var(--ink);text-decoration:none}
 .bo-foot{margin-top:auto;padding:14px 12px 0;border-top:1px solid var(--line);display:flex;flex-direction:column;gap:6px;overflow-wrap:anywhere}
 .bo-main{min-width:0;display:flex;flex-direction:column}
+.bo-side::-webkit-scrollbar{width:0;height:0;display:none}
+.bo-pagefoot{margin-top:auto;padding:22px 26px;border-top:1px solid var(--line);display:flex;gap:20px;flex-wrap:wrap;justify-content:center;font-size:13px}
+.bo-pagefoot a{color:var(--muted)}
+.bo-pagefoot a:hover{color:var(--ink);text-decoration:none}
 .bo-top{display:flex;align-items:center;gap:16px;padding:16px 26px;border-bottom:1px solid var(--line);
   background:rgba(6,10,8,.75);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);position:sticky;top:0;z-index:5}
 .bo-top h2{font-size:20px}