refactor(db): port auth and security handlers to sqlc

- auth.sql: user lookups, counts, register/mirror inserts, profile update
- security.sql: access EXISTS, vulnerability list/metrics/status,
  framework list, latest scan/report, project-id guards
- NULL description/service_id rows stay filtered, matching the original
  scan-error-and-skip behavior
- auth_users probe and filtered audit-log queries stay raw: one is a
  Better Auth table outside the schema, the other is dynamically built
- TestSecurityLiveInvariants covers the access predicate, severity
  ordering, upsert conflict path, and latest-row lookups against live
  Postgres

Authored By: TDvorak <[email protected]>

app/backend/sqlc/queries/auth.sql

@@ -0,0 +1,37 @@
+-- name: GetUserByEmailForAuth :one
+SELECT id, email, password_hash, name, COALESCE(avatar_url, '') AS avatar_url, is_admin, created_at
+FROM users WHERE email = $1;
+
+-- name: CountUsers :one
+SELECT COUNT(*) FROM users;
+
+-- name: CountUsersByEmail :one
+SELECT COUNT(*) FROM users WHERE email = $1;
+
+-- name: UpsertLocalUser :one
+INSERT INTO users (email, password_hash, name, avatar_url, is_admin)
+VALUES ($1, $2, $3, NULLIF($4::varchar, ''), $5)
+ON CONFLICT (email) DO UPDATE
+SET name = EXCLUDED.name,
+    avatar_url = COALESCE(EXCLUDED.avatar_url, users.avatar_url),
+    updated_at = NOW()
+RETURNING id, email, name, COALESCE(avatar_url, '') AS avatar_url, is_admin, created_at;
+
+-- name: InsertUserAdmin :one
+INSERT INTO users (email, password_hash, name, is_admin)
+VALUES ($1, $2, $3, $4)
+RETURNING id, email, name, COALESCE(avatar_url, '') AS avatar_url, is_admin, created_at;
+
+-- name: InsertUser :one
+INSERT INTO users (email, password_hash, name)
+VALUES ($1, $2, $3)
+RETURNING id, email, name, COALESCE(avatar_url, '') AS avatar_url, is_admin, created_at;
+
+-- name: GetUserByID :one
+SELECT id, email, name, COALESCE(avatar_url, '') AS avatar_url, is_admin, created_at
+FROM users WHERE id = $1;
+
+-- name: UpdateUserProfile :exec
+UPDATE users
+SET name = COALESCE($1::varchar, name), avatar_url = COALESCE($2::varchar, avatar_url)
+WHERE id = $3;