ChemSearch v1.13.5 - Periodic table trends & QoL improvements.

What's New

• Added Periodic Table Trends, with property comparisons across all listed elements.
• Added trend metrics for electronegativity, atomic radius, ionization energy, density, melting point, and boiling point.
• Added long-press drag reordering for Tools in both list and grid layouts.
• Added "Did you mean?" search correction when a compound search has no match.
• Added undo actions for clearing recents, deleting recent searches, removing favorites, and deleting downloads.
• Added clearer copy confirmations when tapping identifiers, stats, synonyms, or exported structures.

Improvements & Fixes

• Improved grouped Recent Searches: pinned, today, yesterday, previous 7 days, previous 30 days, and older.
• Improved failed-search suggestions so unrelated PubChem autocomplete results are filtered out.
• Improved Recent Searches layout with cleaner rows, dividers, pin buttons, and delete buttons.
• Improved Periodic Table detail cards with divider lines between entries.
• Improved Periodic Table cards so missing values are hidden instead of shown as placeholders.
• Improved 2D/3D structure controls by removing the large shared pill background.
• Improved the 2D structure viewer with a better background match and icon-only download button.
• Improved the structure share button so it appears as a compact icon-only action.
• Improved Library reference cards by showing a simple Chemical Database entry-count pill.
• Improved Settings and Welcome color scheme pickers with solid one-row color circles.
• Improved Tools reordering behavior so dragged items stay bounded.

Technical Changes

• Added PeriodicTrends.kt for trend metrics, summaries, labels, and normalized values.
• Added unit tests for Periodic Table trend calculations.
• Extended Recent Searches tests for grouping and search-correction filtering.
• Added ViewModel restore helpers for undo actions.
• Added failed-search state fields for correction suggestions.