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]>

package.json

@@ -14,6 +14,7 @@
     "build:css": "postcss css/tailwind.source.css -o css/tailwind.generated.css",
     "build:beacon:bundle": "node scripts/build-beacon.mjs",
     "build:beacon": "npm run build:beacon:bundle && npm run lint:inline-styles",
+    "build:bitcoin-connect": "node scripts/build-bitcoin-connect.mjs",
     "ci:beacon": "npm run build:beacon",
     "format": "prettier --cache --write css/tailwind.source.css css/tokens.css css/docs.css \"docs/**/*.html\" tailwind.config.cjs README.md CONTRIBUTING.md",
     "audit": "node scripts/daily-design-system-audit.mjs",
@@ -57,6 +58,7 @@
     "lint:pool-access": "node scripts/check-direct-pool-access.mjs"
   },
   "devDependencies": {
+    "@getalby/bitcoin-connect": "3.12.3",
     "@playwright/test": "^1.58.2",
     "cssnano": "^7.1.2",
     "fake-indexeddb": "^6.2.5",