chore: prepare release 4.5.1

docs/releases/v4.5.1.md

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+# MTG Python Deckbuilder v4.5.1
+
+## Summary
+Adds an in-app documentation portal with 13 user guides accessible directly at `/help`, contextual help icons throughout the build workflow, and a consistent page header style across all pages.
+
+## Added
+
+### Web documentation portal
+All 13 user guides are now accessible directly in the app at `/help` — no need to navigate to GitHub. A guide index lists every guide with a short description; each guide page renders full markdown with heading anchors for deep linking.
+
+### In-guide table of contents
+Each guide page shows a sidebar with an auto-generated "On This Page" section linking to all headings in the current guide. Collapses to a hamburger toggle on mobile.
+
+### Contextual help links
+Small help icons appear throughout the UI — in the build wizard, bracket selector, owned cards mode, partner selection, and other areas — linking directly to the relevant guide section in a new tab without interrupting the current workflow.
+
+### New guide: Multi-Copy Package
+New dedicated guide covering all multi-copy card archetypes, count recommendations, exclusive groups, bracket interaction, and FAQ.
+
+### Guide enhancements
+All 13 guides end with a See Also section linking to related guides. FAQ sections added to 5 guides (Bracket Compliance, Include/Exclude, Locks/Replace/Permalinks, Owned Cards, Budget Mode). `theme_browser.md` documents the 4-factor badge scoring formula; `bracket_compliance.md` includes a full enforcement matrix.
+
+### Consistent page headers
+All pages now share a unified header style — same font size, description line, and bottom separator — replacing the previous mix of different heading sizes and layouts.
+
+### "Help & Guides" button on home page
+Quick link to the documentation portal from the home page.
+
+## Changed
+
+### Docker: `docs/` volume mount
+`docker-compose.yml` and `dockerhub-docker-compose.yml` now mount `./docs` into the container so documentation edits reflect immediately without a container rebuild.
+
+## Fixed
+
+- **Bug: missing `idx` argument** in `project_detail()` inside `theme_preview.py` caused theme preview pages to crash.
+- **Bug: `build_permalinks` router not mounted** in `app.py` caused all permalink-related endpoints to return 404.
+- **Pydantic V2 deprecation warning** silenced: `DeckExportRequest` now uses `model_config = ConfigDict(...)`.