feat: add wallet-scoped activity tag reads (#136)

[coreyphillips]

Closes #136

Add get_activities_tags(wallet_id) and get_pre_activity_metadata_list(wallet_id), wallet-scoped reads of the tag-backup tables where None returns every scope.

The two tag-backup readers, get_all_activities_tags() and get_all_pre_activity_metadata(), take no wallet id, and the only scoped tag getter is get_tags(wallet_id, activity_id) for a single activity. An app that wants one wallet's tags has to fetch every scope and filter client-side, which makes a one-line app-side .filter { it.walletId == ... } the whole backup-scoping policy for records that go to a remote backup server. Dropping that line is invisible in review and silently widens what leaves the device.

What changed

• ActivityDb::get_activities_tags(Option<&str>) in src/modules/activity/implementation.rs builds the same tag query with an optional WHERE wallet_id = ?1; get_all_activities_tags() now just calls it with None.
• ActivityDb::get_pre_activity_metadata_list(Option<&str>) does the same for pre_activity_metadata; get_all_pre_activity_metadata() delegates to it with None.
• Both scoped readers run the wallet id through the existing normalize_wallet_id, so a blank or whitespace-only scope is a typed error rather than a silent full-table read.
• New UniFFI exports get_activities_tags(wallet_id: Option<String>) and get_pre_activity_metadata_list(wallet_id: Option<String>) in src/lib.rs. The existing unscoped exports are untouched, so no caller breaks.
• README, module README and CHANGELOG document the new calls.

How to test

• cargo test modules::activity, 193 pass, including the four new tests.
• test_get_activities_tags_wallet_scoped and test_get_pre_activity_metadata_list_wallet_scoped each store one record under the default scope and one under a trezor:{64-hex} scope, then assert each scope returns only its own record, that None matches the legacy unscoped getter, and that an unknown scope returns empty.
• test_get_activities_tags_rejects_blank_wallet_id and test_get_pre_activity_metadata_list_rejects_blank_wallet_id cover the whitespace-scope error.
• cargo clippy --all-targets and cargo fmt --check are clean for the touched code.

Notes

Naming: the issue asks for get_activities_tags, which I used verbatim. The metadata equivalent could not drop all_ the same way because get_pre_activity_metadata(wallet_id, search_key, search_by_address) already exists and UniFFI function names are global, hence get_pre_activity_metadata_list. I added new functions rather than changing the existing signatures, so bitkit-android and bitkit-ios keep compiling; the acceptance criterion that unscoped behaviour stays available is met by both the old calls and by passing None. Generated bindings under bindings/ are not regenerated here. This repo does that in separate chore: regenerate bindings commits at release time via build.sh -r, and it needs the iOS/Android cross-compile toolchain, so the new functions are not yet visible to Swift/Kotlin/Python until that step runs. cargo test (full suite) has 11 pre-existing failures, all in modules::blocktank, from api.stag.blocktank.to being unreachable in this environment. They are unrelated to this change; the other 497 pass.