feat: Card Kingdom prices, shopping cart export, and hover panel fixes (#73)

* feat: add CK prices, shopping cart export, and hover panel fixes

* fix: include commander in Buy This Deck cart export

RELEASE_NOTES_TEMPLATE.md

@@ -1,9 +1,26 @@
 # MTG Python Deckbuilder
 
 ## [Unreleased]
-_No unreleased changes yet._
-
-## [4.5.3] - 2026-04-02
 ### Added
-- **SBOM & supply chain provenance**: Every tagged release now attaches source SBOMs (SPDX + CycloneDX JSON) for Python dependencies and a CycloneDX container image SBOM to the GitHub Release assets. Build provenance attestations (SLSA-style) are published for the multi-arch Docker image via the GitHub Attestations API. `provenance: mode=max` is enabled on all arch builds.
+- **Card Kingdom prices**: All price displays now show both TCGPlayer (TCG) and Card Kingdom (CK) prices side by side
+  - Card tile overlays and inline pricing in deck summary, build wizard, and Pickups page
+  - Card hover panel
+  - Upgrade Suggestions table
+  - Alternatives and budget review panels
+  - Card browser grid tiles
+  - Theme detail example cards and commanders
+  - Similar cards panel on card detail pages
+  - Price stat block on individual card detail pages (fetched live via API)
+- **Price source legend**: "TCG = TCGPlayer · CK = Card Kingdom" label added to the deck summary and Pickups pages for clarity
+- **Shopping cart export**: One-click deck purchasing via TCGPlayer and Card Kingdom
+  - **Upgrade Suggestions page**: Per-card checkboxes with select-all toggle; "Open in TCGPlayer" and "Open in Card Kingdom" buttons copy the selected card list to the clipboard and open the vendor's mass-entry page in a new tab
+  - **Finished deck view**: "Buy This Deck" toolbar with the same TCGPlayer and Card Kingdom buttons for the complete deck list (commander + all 99 cards)
+  - Clipboard copy shows a confirmation toast; falls back to a copyable text area if clipboard API is unavailable
+
+### Changed
+- **"Upgrade Suggestions" rename**: The Pickups page and its button in the deck view are now labelled "Upgrade Suggestions" for clarity
+
+### Fixed
+- **Commander hover panel triggered by entire sidebar**: Hovering any element inside the left-hand card preview column (buttons, text, etc.) incorrectly triggered the commander card hover panel; panel now only activates when hovering the commander image or its direct container
+- **Commander hover panel missing prices**: Price information was not shown in the commander card hover panel on the finished deck and run-result views; a price overlay is now attached to the commander image so TCG and CK prices load into the hover panel