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/internal/api/routes.go

@@ -260,6 +260,11 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			authed.GET("/user/profile", handleGetProfile)
 			authed.PUT("/user/profile", handleUpdateProfile)
 
+			// Personal access tokens for CLI/MCP/agent auth.
+			authed.GET("/user/tokens", handleListUserTokens)
+			authed.POST("/user/tokens", handleCreateUserToken)
+			authed.DELETE("/user/tokens/:id", handleDeleteUserToken)
+
 			authed.GET("/notifications", handleListNotifications)
 			authed.POST("/notifications/:id/read", handleMarkNotificationRead)
 			authed.POST("/notifications/read-all", handleMarkAllNotificationsRead)