chore: hygiene sweep — dead code, role race, user lookup, stale files

One pass over the LOW-tier review items plus two folded issues:

- Delete validate_journal_entry (dead since the Fava migration; it
  validated the pre-string-amount model) with its exports, unused
  crud imports, and tests. Beancount validates entries now.
- Migration m006: UNIQUE index on user_roles(user_id, role_id) after
  deduping; assign_user_role inserts with ON CONFLICT DO NOTHING and
  returns the existing assignment — closes the auto-assign
  check-then-act race on concurrent logins.
- Extract _get_username_from_user_id (110 lines in views_api, fresh
  LNbits Database per call inside per-row hot paths) into
  user_lookup.py with one shared core-DB handle, a 60s TTL cache and
  a batch get_usernames API (review #18).
- Receivable-entry responses report CLEARED, matching the flag the
  formatter actually writes; PENDING misled the UI (libra-#35).
- Replace the remaining print() calls in tasks.py with logger.
- get_all_accounts derives valid roots from
  account_utils.ACCOUNT_TYPE_ROOTS instead of a hardcoded tuple, and
  the no-op per-test rate-limit reset is gone (libra-#54).
- Delete migrations_old.py.bak, MIGRATION_SQUASH_SUMMARY.md,
  docs/PHASE*_COMPLETE.md and the rendered .html; .gitignore data/
  (it holds the runtime .lnbits_auth_key secret).
- Track docs/CODE-REVIEW-2026-06.md with finding statuses updated for
  the PR #55-#59 + chore/hygiene series.
- CLAUDE.md notes LNbits pins Pydantic v1: keep .dict(), don't
  "modernize" to .model_dump().

Note: format_payment_entry's is_payable docstring (flagged in review
follow-up) turned out to be consistent with the body — no change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crud.py

@@ -1,4 +1,3 @@
-import json
 from datetime import datetime
 from typing import Optional
 
@@ -18,13 +17,9 @@ from .models import (
     CreateAccount,
     CreateAccountPermission,
     CreateBalanceAssertion,
-    CreateEntryLine,
-    CreateJournalEntry,
     CreateRole,
     CreateRolePermission,
     CreateUserEquityStatus,
-    EntryLine,
-    JournalEntry,
     PermissionType,
     Role,
     RolePermission,
@@ -39,16 +34,6 @@ from .models import (
     UserWithRoles,
 )
 
-# Import core accounting logic
-from .core.validation import (
-    ValidationError,
-    validate_journal_entry,
-    validate_balance,
-    validate_receivable_entry,
-    validate_expense_entry,
-    validate_payment_entry,
-)
-
 db = Database("ext_libra")
 
 # ===== CACHING =====
@@ -1540,10 +1525,15 @@ async def assign_user_role(data: AssignUserRole, granted_by: str) -> UserRole:
         notes=data.notes,
     )
 
-    await db.execute(
+    # The unique index on (user_id, role_id) makes this insert the
+    # arbiter against concurrent assignments (e.g. two simultaneous
+    # logins both auto-assigning the default role). rowcount 0 means
+    # the assignment already exists — return it (idempotent).
+    result = await db.execute(
         """
         INSERT INTO user_roles (id, user_id, role_id, granted_by, granted_at, expires_at, notes)
         VALUES (:id, :user_id, :role_id, :granted_by, :granted_at, :expires_at, :notes)
+        ON CONFLICT (user_id, role_id) DO NOTHING
         """,
         {
             "id": user_role.id,
@@ -1555,6 +1545,14 @@ async def assign_user_role(data: AssignUserRole, granted_by: str) -> UserRole:
             "notes": user_role.notes,
         },
     )
+    if result.rowcount == 0:
+        existing = await db.fetchone(
+            "SELECT * FROM user_roles WHERE user_id = :user_id AND role_id = :role_id",
+            {"user_id": data.user_id, "role_id": data.role_id},
+            UserRole,
+        )
+        if existing:
+            return existing
 
     return user_role