feat: Python bindings via PyO3 + maturin (resolves #138)

[Johnson-f]

Summary

Adds a new workspace crate finance-query-python that compiles the Rust library
into a native Python extension via PyO3 + maturin, published to PyPI as
finance-query-py. Closes #138.

Verified live against Yahoo Finance / Alternative.me / SEC EDGAR — 51/51 surface
tests pass (see Test plan below).

What ships

Surface	Coverage
Ticker	17 methods: new, builder, symbol, quote, chart, chart_range, dividends, splits, capital_gains, financials, news, recommendations, edgar_submissions, 3× clear_cache*
TickerBuilder	7 chainable setters + async build()
Tickers (batch)	new, symbols, __len__, quotes, charts + BatchResult { data, errors }
finance.*	12 free functions: search, screener, trending, fear_and_greed, lookup, market_summary, hours, sector, currencies, news, industry, exchanges
Enums	11 (Interval, TimeRange, Frequency, StatementType, Region, ValueFormat, Sector, Screener, ExchangeCode, Industry, FearGreedLabel)
Exceptions	6 typed (FinanceQueryError + NetworkError, RateLimitError, SymbolNotFound, ParseError, ConfigError)
Models	~110 PyModel-derived wrappers across all model modules; to_dict() everywhere, to_dataframe() on Chart, Candle, Dividend, Split, CapitalGain, OptionContract, FinancialStatement, News, SearchQuote, TrendingQuote, etc.
Helpers	enable_logging(level), edgar_init(email), edgar_init_with_config(...)

Architecture

• PyModel proc-macro in finance-query-derive (behind a new python feature) generates Py* wrappers from existing Rust structs. Attributes: eq, rename, dataframe = "columns", dataframe_from = "<field>". Handles primitives, String, Vec<T>, Option<T>, HashMap<K, V>, nested PyModel types, FormattedValue<T> (via concrete PyFormattedValueF64/I64/U64/String), and serde_json::Value (auto-pythonized).
• Core crate (finance-query) gains an optional python feature pulling in pyo3 0.27, pyo3-polars 0.26, pythonize 0.27. Default builds unchanged — Rust users pay nothing.
• Async bridging via pyo3-async-runtimes 0.27 on a single shared tokio runtime initialized at module import.
• abi3-py39 wheels — one wheel per platform covers Python 3.9 → 3.13+.

Repository layout

finance-query-python/              # NEW workspace crate (cdylib)
├── src/                           # lib.rs, runtime.rs, error.rs, ticker.rs,
│                                  # tickers.rs, finance.rs, enums.rs, edgar.rs,
│                                  # logging_bridge.rs, models.rs
├── finance_query/                 # pure-Python package
│   ├── __init__.py
│   ├── _finance_query.pyi         # type stubs (mypy --strict clean)
│   └── py.typed
├── docs/examples/quickstart.ipynb # Jupyter walkthrough
├── tests/                         # pytest: unit + smoke + parity layers
├── Cargo.toml, pyproject.toml, Makefile, README.md

finance-query-derive/              # extended with PyModel derive
src/constants_py.rs                # NEW: 10 Python enum mirrors
src/models/quote/formatted_value.rs# NEW: PyFormattedValue* family
src/models/**/*.rs                 # ~50 files annotated with #[derive(PyModel)]
tools/record-parity-fixtures/      # NEW: Rust binary for cross-lang fixtures
.github/workflows/python-wheels.yml# NEW: 6-job CI (test, parity, build×3, smoke×20, publish)
docs/migration-from-yfinance.md    # NEW: yfinance → finance-query-py cheat sheet

Phase 2 follow-ups (not in this PR)

• ticker.options() — Options wraps pub(crate) OptionChainContainer; needs hand-written wrapper or making the inner type public.
• ticker.edgar_company_facts() — CompanyFacts.HashMap<String, FactsByTaxonomy> (tuple struct value); PyModel needs to support that combo.
• Streaming PriceStream (always planned for Phase 2).
• backtesting, risk namespace ergonomics.

Test plan

• cargo check --features python — clean (40 doc-comment warnings, no errors)
• cargo test -p finance-query-derive --features python — 3 trybuild tests pass (ui_simple, ui_collections, ui_full)
• cd finance-query-python && maturin develop --release — builds wheel cp39-abi3-<platform>
• python3 -m pytest -m "not network" — 34 passed
• python3 -m mypy — clean against the stubs
• Live network test — 51/51 (see comment below for full output)
• CI: 5 platforms × abi3 → smoke matrix on 4 OS × 5 Python versions
• PyPI trusted-publisher one-time setup before first finance-query-py-v* tag (see finance-query-python/README.md → Releasing)

Quickstart for reviewers

cd finance-query-python
maturin develop --release
python3 -c "
import asyncio
from finance_query import Ticker, Interval, TimeRange

async def main():
    t = await Ticker.new('AAPL')
    q = await t.quote()
    print(f'{q.symbol}: {q.short_name} @ \${q.regular_market_price.raw}')
    chart = await t.chart(Interval.OneDay, TimeRange.OneMonth)
    print(chart.to_dataframe().head())

asyncio.run(main())
"

🤖 Generated with Claude Code

[Verdenroz]

I hope to look at this around Wednesday, worst case Friday as the multi-provider architecture is revealing a lot of tech debt that I'm only reaping now 😭

[Verdenroz]

Finally figured out a decent structure. Given the sheer scope of the refactoring, it might honestly be best to just checkout from master on a fresh branch.

If you prefer to continue working on this branch, I can help rebase your branch if needed. Sorry for the conflicts 🙏 !