feat(wallets): extensionBrowsers schema, column metadata and validation (DBIP #3713)

[foxxx009]

Closes #3713 (tools side)

Problem

supportedPlatforms identifies delivery formats (e.g. "Browser Extension"), not the desktop browser products a provider currently supports, so users cannot answer "does this wallet have a maintained Firefox extension?" from the data.

Changes

• tools/schema.json: optional extensionBrowsers property on wallets — JSON array or null, items restricted to the initial vocabulary Brave/Chrome/Edge/Firefox/Opera/Safari, uniqueItems: true.
• meta/columns.json: extensionBrowsers metadata (arrayPopover, capabilities group, searchableMultiSelect filter).
• tools/csv_to_json.py: validate_extension_browsers() — rejects nonarrays, unknown/lowercase names and duplicates, and enforces canonical alphabetical ordering; wired into both canonical offers and every expanded network listing.

Validation covered (per DBIP #3713 §Migration 5)

• NULL accepted (unknown / inherit)
• [] accepted (explicit: no desktop extension documented)
• MetaMask ["Brave","Chrome","Edge","Firefox","Opera"] accepted
• Phantom ["Chrome"] accepted
• duplicates rejected
• lowercase alias rejected
• unknown browser rejected
• non-canonical ordering rejected
• converted/expanded listings validated through the existing CSV-to-JSON pipeline (validate_csv.py → csv_to_json.py → validate.py all green locally)

Data side: paired PR adds the column to the 92 wallet tables and seeds only the two evidence-backed canonical rows.

Rewards address: 0x2409b47a530be3831158f10b08ac93f7d08c1ff2