Add URL rewriting for imported SQL data

Adds a `db-apply` command that reads `db.sql`, rewrites URLs in decoded
base64 string values using wp-php-toolkit structured processors (no regex),
and executes statements against a target MySQL database with cursor-based
resumability.

Key components:
- Base64ValueScanner: extracts FROM_BASE64('...') values from SQL
- ContentClassifier: detects serialized PHP (skip), JSON, or text/HTML
- SqlValueUrlRewriter: rewrites URLs via BlockMarkupUrlProcessor/URLInTextProcessor
- SqlStatementRewriter: orchestrates per-statement rewriting
- DomainCollector: discovers HTTP/HTTPS domains during db-sync download

Domain discovery runs inline during db-sync, saving results to
.import-domains.json. The db-apply command uses WP_MySQL_Naive_Query_Stream
(vendored from WordPress/sqlite-database-integration#264) for streaming
SQL execution with periodic state checkpoints.

72 unit tests covering all components. E2E test scaffolding included.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: adamziel

composer.json

@@ -6,7 +6,9 @@
     "require": {
         "php": ">=7.4",
         "ext-pdo": "*",
-        "ext-pdo_mysql": "*"
+        "ext-pdo_mysql": "*",
+        "wp-php-toolkit/data-liberation": "^0.4",
+        "wp-php-toolkit/html": "^0.4"
     },
     "require-dev": {
         "phpunit/phpunit": "^10.0",