feat: personal access tokens with scoped bearer auth

Add cnp_ personal access tokens so the CLI, MCP server, and external
agents authenticate without a browser session — the agent-first spine
from ROADMAP2 phase A. Modeled on agent_auth_tokens: raw token shown
once, only SHA-256 hash stored.

- user_tokens table (goose migration + sqlc), name/prefix/scope/expiry,
  owner-scoped revoke, last_used_at stamping
- middleware: cnp_ bearer resolution, read scope gates mutations with
  403 SCOPE_INSUFFICIENT, non-admin scopes cap is_admin even for admin
  owners — a token never outranks its scope or its owner
- GET/POST/DELETE /api/v1/user/tokens + OpenAPI + generated types
- Settings UI: create with scope/expiry pickers, one-time token display
  with copy, list with last-used/expiry, confirm-revoke
- docs: OPERATIONS.md section, README feature line

Verified end-to-end against live Postgres: create/list/revoke, read
scope blocks PUT (403), write PAT on admin owner blocked from admin
routes (403), admin scope works, revoked token returns 401.

Authored By: TDvorak <[email protected]>

app/backend/sqlc/queries/user_tokens.sql

@@ -0,0 +1,24 @@
+-- name: CreateUserToken :one
+INSERT INTO user_tokens (user_id, name, key_prefix, token_hash, scope, expires_at)
+VALUES ($1, $2, $3, $4, $5, $6)
+RETURNING *;
+
+-- name: ListUserTokens :many
+SELECT * FROM user_tokens
+WHERE user_id = $1 AND revoked_at IS NULL
+ORDER BY created_at DESC;
+
+-- name: GetUserTokenByHash :one
+SELECT * FROM user_tokens
+WHERE token_hash = $1
+  AND revoked_at IS NULL
+  AND (expires_at IS NULL OR expires_at > NOW())
+LIMIT 1;
+
+-- name: TouchUserToken :exec
+UPDATE user_tokens SET last_used_at = NOW()
+WHERE id = $1 AND revoked_at IS NULL;
+
+-- name: RevokeUserToken :execrows
+UPDATE user_tokens SET revoked_at = NOW()
+WHERE id = $1 AND user_id = $2 AND revoked_at IS NULL;

app/backend/sqlc/schema.sql

@@ -204,3 +204,16 @@ CREATE TABLE notifications (
     read_at TIMESTAMP WITH TIME ZONE,
     created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
 );
+
+CREATE TABLE user_tokens (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    name VARCHAR(255) NOT NULL,
+    key_prefix VARCHAR(16) NOT NULL,
+    token_hash TEXT NOT NULL UNIQUE,
+    scope VARCHAR(20) NOT NULL DEFAULT 'write',
+    expires_at TIMESTAMP WITH TIME ZONE,
+    last_used_at TIMESTAMP WITH TIME ZONE,
+    revoked_at TIMESTAMP WITH TIME ZONE,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);