Add MCP server so Claude and ChatGPT can read and write drink data

Exposes the collection over the Model Context Protocol at /api/mcp, with 22
tools covering drinks, ratings, bar inventory, recipes, wishlist and taste
preferences, plus search/fetch aliases for ChatGPT's deep-research mode.

Authentication is a bearer token, the app's first header-borne credential -
every other route derives identity from the NextAuth cookie, which a machine
client cannot present. /api/mcp sits under the middleware's /api exclusion so
it can answer a JSON 401 with an RFC 9728 WWW-Authenticate challenge instead
of an HTML redirect to /login.

Tokens are stored as a SHA-256 hash rather than plaintext like Invite.token
and PasswordReset.token. Those are single-use and short-lived; this one is
long-lived and grants read/write over a whole collection, and the nightly
pg_dump keeps 14 days of history. Not encrypt(), which is reversible AES and
right only for outbound keys we must replay; not bcrypt, which cannot be
indexed and would turn verification into a table scan per request.

verifyMcpToken joins User.status on every call, mirroring the jwt callback, so
suspending a member kills their MCP access immediately rather than leaving the
token as a documented way to outlive suspension. It fails closed on a database
error, deliberately unlike the jwt callback, which keeps the session because a
throw there would sign out every user at once.

No tool reaches the Switchboard gateway. Claude and ChatGPT are language
models already, so they can reason over a bar inventory without the app paying
to do it a second time, and a remote client looping a vision call is not a
failure mode worth having. Account deletion, restore, gateway keys, admin
routes and shared-list creation are excluded too.

The OAuth models ship now but are unused; the token endpoint will write the
same McpAccessToken rows, so adding it later touches no verification code.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1Ee4Mc1X1SX8HgYa52zu7

src/lib/mcp/config.ts

@@ -0,0 +1,61 @@
+/**
+ * Static configuration for the MCP server.
+ *
+ * The origin is read from NEXTAUTH_URL rather than derived from the incoming
+ * request. `publicOrigin()` in src/lib/origin.ts explains why for links; here it
+ * matters more. RFC 9728 requires the `resource` field of the protected resource
+ * metadata to match the URL the user typed into their client byte for byte, and
+ * RFC 8414 requires the OAuth `issuer` to equal the origin it was discovered at.
+ * Deriving either from X-Forwarded-* means a proxy misconfiguration shows up as a
+ * silent connector failure with no useful error, so it is pinned to config instead.
+ */
+
+export const MCP_SERVER_NAME = "drinktracker"
+export const MCP_SERVER_VERSION = "1.0.0"
+
+/** Path the MCP endpoint is mounted at. Clients are given the full URL. */
+export const MCP_PATH = "/api/mcp"
+
+/**
+ * Scopes. Two axes, read and write, over two halves of the data:
+ *
+ *   drinks:*  the collection and journal - drinks, ratings, wishlist, preferences
+ *   bar:*     the inventory and what can be made from it - bar items, recipes
+ *
+ * Kept deliberately coarse. A consent screen listing eight scopes is a consent
+ * screen nobody reads.
+ */
+export const MCP_SCOPES = [
+  "drinks:read",
+  "drinks:write",
+  "bar:read",
+  "bar:write",
+] as const
+
+export type McpScope = (typeof MCP_SCOPES)[number]
+
+/** Everything a read-only connection gets. The default when minting a token. */
+export const MCP_READ_SCOPES: McpScope[] = ["drinks:read", "bar:read"]
+
+/** Full access. */
+export const MCP_ALL_SCOPES: McpScope[] = [...MCP_SCOPES]
+
+export function isMcpScope(value: string): value is McpScope {
+  return (MCP_SCOPES as readonly string[]).includes(value)
+}
+
+/** Public origin, no trailing slash. */
+export function mcpBaseUrl(): string {
+  const configured = process.env.NEXTAUTH_URL
+  if (configured) return configured.replace(/\/$/, "")
+  // Only reachable in local development, where NEXTAUTH_URL is usually unset.
+  return "http://localhost:3000"
+}
+
+/**
+ * The resource identifier for this MCP server, which is also the URL a user
+ * pastes into claude.ai. Must match their input exactly.
+ */
+export function mcpResourceUrl(): string {
+  return `${mcpBaseUrl()}${MCP_PATH}`
+}