docs(migration): update migration guide to v1.4 with PHP deprecation status
- bump documentation version from v1.3 to v1.4
- update PHP file status to show both "migrated" and "deprecated"
indicators in the files table
- mark api.php to return 410 Gone, login.php for 301 redirect
- change task 3.6 status from "in progress" to "waiting for execution"
with provided command: rmdir /s /q php
- update Phase 3 progress from 90% to 95%, overall progress from 95% to 98%
- add v1.4 changelog entry with documentation updates and status changes
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