feat(messenger): add a Message shortcut to a member's profile

[bmc08gt]

A group member's profile had no direct way to reach that person. ChatProfileScreen's header now has a round Message shortcut under the join date, above the Report and Block rows. It pushes AppRoute.Messaging.Chat(ChatIdentifier.ByUser(...)), the same route "View in Chat" uses from transaction details. It goes through LocalCodeNavigator, like the Report row, so the DM opens as a top-level route over the group chat.

Send Cash, held back

A second Send Cash shortcut is built but commented out in ProfileShortcuts. Everything behind it stays wired so it can come back by uncommenting:

• AppRoute.Messaging.Chat.openSendCash opens the DM with send cash started: the fee sheet if this payment creates the DM, the keypad if it already exists.
• OnSendCash drops the event while participant is null. It also falls back to the keypad before the opening fee loads. So the chat can't dispatch it on first composition the way openKeyboard does. ChatViewModel.State.sendCashReady becomes true once the participant is set and the chat's existence and fee agree: it exists with no fee, or it doesn't exist and the fee has resolved.
• StartSendCashOnceReady dispatches once on that edge, behind a rememberSaveable flag, so rotation or returning from the payment step doesn't fire it again.
• isChatInitialized now reads from a nullable chatExistence flow, to tell "not answered yet" apart from "no DM".
• The 22sp condensed symbol size in SendCashButton is now CondensedSymbolFontSize, for the shortcut to share.

Visibility

profileShortcutRecipient returns the TipUser to message, or null to hide the shortcut:

• hidden when the chat is a TIP_DM, because a DM's profile is the other person in it, so the shortcut would only reopen that chat
• hidden on the viewer's own profile (userManager.accountId)
• hidden for anyone who isn't a TipUser, since ByUser needs a user id

Blocked users aren't checked.

Layout

• 45dp circle filled with surfaceVariant, holding a 20dp white Material Symbols chat_bubble (filled).
• The label is textSmall in textSecondary, 5dp below the circle, in a 100dp column.
• The shortcut sits 25dp below the join date and 25dp above the first row's text. The first menu row already has a 25dp inset, so the header drops its bottom padding when the shortcut shows.
• The empty mute line above would otherwise add about 28dp. ChatMuteStatusChip now takes reserveSpace, which is off when the shortcut shows. That only happens on a group member's profile, which has no Mute row to change it while the screen is open.

Tests

• ProfileShortcutRecipientTest: the visibility rule.
• ChatViewModelStateTest: isSendCashReady across participant, existence and fee.
• StartSendCashOnceReadyTest: waits for ready, fires once, and doesn't refire after recreation.
• ChatIdentityScreenshotTest: the header with the shortcut.