bug(frontend): inline column filters missing from RI Exchange and Plans tables (regression after #166/PRs #789/#791)

[cristim]

Repro for RI Exchange

1. Navigate to Inventory & Coverage > RI Exchange.
2. Look for inline per-column filter controls on the Active Convertible RIs or Reshape Recommendations table headers.

Repro for Plans

1. Navigate to Plans.
2. Look for inline per-column filter controls on the plans table headers.

Expected

Both tables have inline per-column filter controls (matching the pattern implemented for Opportunities, Purchases, and History tables).

Actual

No inline column filters are present on either the RI Exchange or Plans tables.

Context

Issue #166 ('refactor(frontend): extract column-filter primitives into a shared module') was closed as done, with PRs #789 (RI Exchange), #791 (Plans), and #790 (History, still open) merged. The RI Exchange (#789) and Plans (#791) filters are not working despite those PRs merging.

Sheet reference

Bugs and improvement suggestions tab, rows 532 (RI Exchange) and 534 (Plans).

[cristim]

Partial resolution: the RI Exchange inline column filters (genuinely missing) are restored by #1435. The Plans table filters were independently verified to already exist and be functional on main (plans.ts renders filterBtn per column + applyPlansColumnFilters + plans-column-filters.test.ts) — the Plans repro (QA sheet row 534) appears stale. #1435 uses refs #1414 (not closes) so this stays open for QA to re-verify the Plans table against the current build; close if it filters correctly.