[bmc08gt]

Syncs flipcash2 protos from 1897108a to 733ea7f9 (#147, #148, #149) and adds the 0.20.0 changelog entry. community.v1 is new; activity.v1, chat.v1, intent.v1 and messaging.v1 moved. Everything is additive:

• community.v1.Community with one RPC, GetCommunity(mint), returning CommunityMetadata or NOT_FOUND.
• Paid reaction boosts: ChatMetadata.reaction_boost (oneof field 5), boost_usd on Reactor, EmojiReaction and ReactionUpdate, ReactionUpdate.actor_boost_usd, and BoostedReaction on the sent/received crypto notifications.
• chat.v1.Metadata.holdings_summary (field 18) for public groups gated on a single Flipcash currency.

Two enums gained a case, both appended last, so no existing value moved: ReactionUpdate.Action.BOOSTED = 3 and RemoveReactionResponse.Result.CANNOT_REMOVE_BOOSTED = 3. Reactor and reaction lists now sort boosted entries first; that is a comment change, not a wire change.

Release this as 0.20.0 after merge, after ocp-client-protocol 0.8.0 (code-payments/ocp-client-protocol#11): a boost that pays two people is an ocp SendPublicMultiPayment. Both app PRs consume the two packages on one branch:

• Android: feat(flipcash): adopt ocp 0.8.0 and flipcash2 0.20.0 contracts code-android-app#1799 (draft)
• iOS: feat(flipcash): adopt ocp 0.8.0 and flipcash2 0.20.0 contracts code-ios-app#1078 (draft)