feat(wallet): Bitcoin Connect NWC "Connect wallet" flow [LOCAL — flag ON, do not push as-is]

Phase 0+1 of docs/bitcoin-connect-plan.md (#61). Adds Alby's Bitcoin Connect as a
one-tap NWC connect front-end that feeds bitvid's EXISTING wallet pipeline; manual
URI entry stays as the backup.

- Vendored: pinned @getalby/[email protected].3 bundled by
  scripts/build-bitcoin-connect.mjs → vendor/bitcoin-connect.bundle.min.js (esbuild,
  browser ESM). crypto-shim aliases the L402-only `import('crypto')` bitvid never
  calls. `npm run build:bitcoin-connect` rebuilds it.
- Flag: FEATURE_BITCOIN_CONNECT wired like FEATURE_AUDIO_INGEST
  (instance-config → config → constants).
- UI: a "Connect wallet" button in the Wallet Connect pane (hidden unless the flag
  is on); the manual URI field stays below as the backup.
- Controller: ProfileWalletController.handleBitcoinConnect() lazy-imports the bundle
  (only on click — the ~700KB never touches the main bundle), inits NWC-only with
  least-privilege requestMethods and persistConnection:false, then on onConnected
  extracts provider.client.nostrWalletConnectUrl → the SAME validate→save path as
  the manual field → disconnect() so bitvid solely holds the spending secret. The
  URI is never logged.

NOTE: config/instance-config.js FEATURE_BITCOIN_CONNECT is TRUE for local testing
only. Reset to false (shipping default) before pushing/deploying. Local commit;
not pushed, not deployed.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

components/profile-modal.html

@@ -860,6 +860,30 @@
                 <p class="text-sm text-muted">
                   Connect a Nostr Wallet Connect (NWC) compatible wallet to zap creators directly from bitvid.
                 </p>
+                <div id="profileWalletBitcoinConnectRow" class="hidden space-y-2">
+                  <button
+                    id="profileWalletBitcoinConnect"
+                    type="button"
+                    class="btn focus-ring inline-flex items-center gap-2"
+                  >
+                    <svg
+                      class="h-4 w-4"
+                      viewBox="0 0 24 24"
+                      fill="none"
+                      stroke="currentColor"
+                      stroke-width="2"
+                      stroke-linecap="round"
+                      stroke-linejoin="round"
+                      aria-hidden="true"
+                    >
+                      <path d="M13 2 4 14h6l-1 8 9-12h-6l1-8Z"></path>
+                    </svg>
+                    Connect wallet
+                  </button>
+                  <p class="text-xs text-muted">
+                    One-tap connect via Bitcoin Connect (NWC) — or paste a connection manually below.
+                  </p>
+                </div>
                 <div class="space-y-4">
                   <label class="block text-sm text-muted-strong" for="profileWalletUri">
                     <span class="mb-2 block font-medium">Wallet Connect URI</span>