feat(ingestion): add DOCX/CSV/XLSX parsing and fixed-size chunking (ADR-0018)

Adds src/application/ingestion/ -- Persian normalization, DOCX body
walk with structural data/layout table classification, CSV/XLSX row
rendering, and fixed-size token chunking (cl100k_base, 400/60/512) --
as pure functions per ADR-0015, tested against real production
documents (asia_data_sample, kept out of the repo). ADR-0018 records
where this diverges from ADR-0004 (fixed-size default, no invented
headings/tree, structural table classification, header-provable
labeling only). Plan 001's scope line is corrected from CSV-only to
DOCX/XLSX/CSV, and CLAUDE.md's stale project-status paragraph is
updated to match current implementation state.

pyproject.toml

@@ -11,10 +11,13 @@ dependencies = [
     "fastapi[standard]==0.141.1",
     "langgraph>=1.2.10",
     "minio>=7.2.20",
+    "openpyxl>=3.1.5",
     "pydantic-settings>=2.15.0",
+    "python-docx>=1.2.0",
     "qdrant-client>=1.19.0",
     "sqlalchemy>=2.0.51",
     "structlog>=26.1.0",
+    "tiktoken>=0.13.0",
 ]
 
 [dependency-groups]