Add SI-prefix-aware sorting column for parts tableFeature/si value sort

[wschopohl]

Summary

• Adds an optional "SI Value" column to the parts table that parses numeric values with SI prefixes (p, n, u/µ, m, k/K, M, G, T) from part names and sorts by the resulting physical value
• Useful for electronic components where alphabetical sorting produces wrong results — e.g. 100nF, 10pF, 1uF sort as 10pF < 100nF < 1uF
• The column displays the parsed float value, or an empty cell for non-matching names
• Only matches numbers at the start of the name — part numbers like "MCP2515" or "Crystal 20MHz" are not affected
• Supports both dot and comma decimal separators (European locale)
• Falls back to NATSORT for parts without SI values, so they sort alphabetically rather than arbitrarily
• Opt-in: not in default columns, users enable it via the column visibility button

Implementation

• New SiValueSort DQL function with platform-specific SQL for PostgreSQL (POSIX regex), MySQL/MariaDB (REGEXP_SUBSTR), and SQLite (PHP callback via the existing middleware)
• 33 unit tests covering all platforms, SI prefixes, edge cases, and sort order verification

Test plan

• Unit tests pass (33 tests, all platforms)
• PHPStan level 2 passes
• Tested against real parts database with SQLite

[wschopohl]

For completeness, here is a screenshot showing how SI Value improves table ordering. It uses the value from 'Name' under the hood, extracting leading numbers with SI prefixes.