feat: expose volume, liquidity, date, and tag filters on list commands

[qtzx06]

Summary

• Wires through volume, liquidity, date range, and tag filter params that the SDK already supports but markets list and events list weren't exposing
• Users no longer need to over-fetch and filter client-side to find specific markets

Closes #38

New flags on markets list and events list

Flag	Description
--volume-min / --volume-max	filter by trading volume
--liquidity-min / --liquidity-max	filter by liquidity
--start-date-min / --start-date-max	filter by start date
--end-date-min / --end-date-max	filter by end date
--tag	filter by tag ID (markets) or tag slug (events, already existed)

Example

# find high-volume markets created this month
polymarket markets list --volume-min 1000000 --start-date-min 2026-03-01T00:00:00Z

Test plan

• cargo test — 131 tests pass
• cargo clippy -- -D warnings — clean
• cargo fmt --check — clean
• Verified --help output shows new flags correctly

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Note

Low Risk
Low risk: this only adds new CLI flags and forwards them into existing SDK request builders without changing core business logic or data writes.

Overview
Adds new filtering flags to events list and markets list for volume and liquidity ranges plus start/end date ranges, wiring them through to the underlying EventsRequest/MarketsRequest builders.

Also exposes a --tag filter on markets list (tag ID) and keeps events list tag filtering (tag slug), enabling server-side filtering instead of client-side post-processing.

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