Restore Market Filter with Custom Expression Parser

[GODrums]

Closes #400

Step 3 of #395

Adds a compatibility layer to support our filter container in the Steam Market Beta.

Due to React's self CSP, it also replaces filtrex with a custom expression parser supporting the same input syntax. Architected with Opus 4.8, reviewed by Fable 5. Tested all variables and operators manually

Screenshots

!https://github.com/user-attachments/assets/1d296ca3-3ec6-4eed-88c5-7ec2f2d5bdef

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Note

Medium Risk
Replaces the entire filter expression engine and broadens valid return types, so subtle syntax or truthiness mismatches vs filtrex could affect highlights across classic and beta market pages.

Overview
Brings CSFloat highlight filters back on the Steam Market beta by mounting the existing filter UI above the React listing grid and wiring beta listing cards to the same gFilterService highlighting used on the classic market.

filtrex is removed and replaced with an in-tree compile_expression tokenizer/parser/evaluator so filter syntax still works under React’s stricter CSP. Filter now compiles through that module; isValidReturnValue treats any non-Error result as valid instead of only booleans and 0/1.

Beta BetaListingEnhancer derives price from listing fiber props, subscribes to filter updates, and paints each card’s background/text when a filter matches.

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