Return clickable file:// locations for generated HTML/PDF reports

[YashvantHange]

What & why

The report tools write files to disk but only surface a bare path string, so a user has to hunt the path down and open it manually. This makes each generated file's location a clickable file:// link — for the HTML and the PDF — so clicking it opens the file in the default app (browser for HTML, viewer for PDF). Nothing opens on its own; the file opens on click.

Stacked on #23 (base = feat/auto-html-modern-report) because it builds on that branch's html_report_path plumbing. Retarget to main once #23 merges.

Changes

• export.py — one helper file_url(path) = absolute, percent-escaped file:///… (reused by the headless-Chrome loader, so a click opens exactly the file that was written). save_html/save_pdf unchanged — no side effects.
• models.py — new ExportedFile; ExportResult gains file_url + a files list (a PDF export lists both the pdf and its html sidecar); AnalysisReport gains html_report_url.
• server.py — analyze_company's auto-HTML records html_report_url; export_report returns file_url + files for html and pdf.
• cli.py — investo analyze prints the clickable file:// URL for every written artifact (and the html sidecar's URL for --pdf). No --no-open flag — nothing auto-opens.

Verification

• ruff check ., mypy, pytest -q — all green (285 tests; added file_url + URL-surfacing coverage).
• Live CLI run confirmed the output, e.g.:

  Wrote PDF report to …\rel_links.pdf  (chrome.exe (headless))
    Open: file:///C:/…/rel_links.pdf
    HTML: file:///C:/…/rel_links.html
  

• Clicking a printed file:// link opens the report in the default app.