Filter history: foundation (feature flag + Room persistence)

[AdamGrzybkowski]

Part of WOOMOB-3326 — WOOMOB-3824

Description

First of a stack of PRs adding filter history to the order and product lists (feature request WOOMOB-31, matching the iOS implementation). Everything is gated behind the new FILTER_HISTORY feature flag and is not user-visible yet.

This foundation PR adds the persistence layer only — no UI:

• New FILTER_HISTORY feature flag (woo_filter_history, debug-on).
• A Room-backed, per-site FilterHistory table (entity + DAO) added to FluxC's WCAndroidDatabase (version 91 → 92, one auto-migration), following the Support Chat bookmark precedent.
• A main-app FilterHistoryRepository exposing per-surface observe/save/remove/clear, with dedup + newest-first + unlimited history (matching iOS), and a SavedFilter domain model.

The stored payload is an opaque, per-surface serialization (decoded by the order/product screens in later PRs), so adding new filters later needs no schema migration.

Test Steps

No user-facing behaviour. CI green is the bar:

• ./gradlew :libs:fluxc-plugin:testDebugUnitTest --tests "*FilterHistoryDaoTest*" — covers dedup / newest-first / delete / clear / per-site isolation on an in-memory DB.

Stacked PRs

This is PR 1 of 4, targeting trunk. The rest target the previous branch:

1. (this) foundation — trunk
2. shared filter history screen
3. order list integration
4. product list integration

• I have considered if this change warrants release notes — none needed (behind feature flag, not user-facing).

[dangermattic]

	1 Warning
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by 🚫 Danger

[claude]

AI Code Review - No issues found. The changes look good.

This is a well-scoped foundation PR (feature flag + Room persistence for filter history). The DB version bump 91→92 adds a brand-new empty table via AutoMigration(91, 92), which Room handles automatically, and the schema 92.json is committed — the migration is deploy-safe. The dedup-by-payload contract (unique index on (localSiteId, filterType, payload) + OnConflictStrategy.REPLACE) is implemented correctly and well covered by the DAO tests (dedup/bump, site isolation, clear scoping, newest-first ordering). No correctness, security, or backwards-compatibility concerns.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Build Number	778
	Version	25.4-rc-1
	Application ID	com.woocommerce.android.prealpha
	Commit	06d5063
	Installation URL	7h3tsn9q0i2s8

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