feat(chat): show a person card for Flipcash profile links

[bmc08gt]

Links to a Flipcash profile — flipcash.com/<handle>, flipcash.com/<uuid>, and legacy /tip/<uuid> on the Flipcash hosts — now render in chat as a person card instead of underlined text. This ports code-payments/code-ios-app#872 and #879, plus the stray-punctuation split fix from #880.

Design decisions

Classification

• Person links classify through the existing AppRouter (DeeplinkType.Tipcard / TipcardByUsername), so the reserved profile paths (download, privacy, terms, support, help, about, blog, legal, currencycreator, app, api, assets, fonts, icons, js, v1, pool) stay website links. iOS copied that list from Android, and AppRouterTest already covers it. The messenger classifier test uses a fake router, which mirrors the list and points at AppRouterTest, because AppRouter is internal to its module.
• Non-Flipcash hosts (e.g. discord.gg/x) don't produce a card.
• The shared link_detection.json fixture still expects no card for its tip-card-by-id vector. As on iOS, that vector is marked "ahead of fixture" rather than the fixture being edited here.

Lookup (UserLinkLookup)

• It fetches the profile with ProfileController.getProfileForUser / getProfileForUsername only. Nothing is reused from the tip flow: no profile caching, no bill overlay, no navigation.
• A profile with no userId (an unclaimed handle) is not found. A thrown error is also not found, and isn't memoized, so the card retries the next time it appears. A found profile is memoized per identity, the same way the group card is.
• Own-link detection compares against userManager.accountId.
• The card reads only Profile: picture blurhash, picture, display name, @username, and joinedAt. It doesn't show minDmChatInitFee (the DM's fee sheet still handles payment) and doesn't read tip card colours.

Tap (ChatAction.OpenUser)

• The whole card is the tap target. For someone else, it pushes AppRoute.Messaging.Chat(ChatIdentifier.ByUser(...)) on the current stack, the same way the group card pushes its chat.
• Your own link calls rootNavigator.navigateAll(listOf(AppRoute.Tabs.Menu)). That's where your tip card lives on Android, and where the own-card deep link and scanning your own card already go.
• A link to the person you're already DMing does nothing. A not-found card has no tap action, but long-press still reaches the transcript.

Look (UserLinkCard.kt, constants in UserLinkCardDefaults mirroring iOS LinkUserCardContent.Layout)

• The row hugs its text, capped at the bubble width: avatar 44, gap 12, padding 10 top/bottom, 10 leading, 16 trailing, line gap 2.
• At font scale ≥ the accessibility threshold, the avatar sits above the text and every line wraps with no ellipsis.
• The backdrop is the blurhash, cropped to fill, under black at 0.6 (TINT_OPACITY, provisional pending design sign-off). With no blurhash, the tint sits over CodeTheme.colors.background. The photo itself is never the background.
• The backdrop is drawn in drawBehind rather than Modifier.paint: with bounded constraints, paint(sizeToIntrinsics = false) raises the minimum size to the maximum, and the card filled the whole bubble.
• The shape and border reuse GroupInviteCardDefaults.SHAPE / STROKE, the group card's radius 12 and white 0.1 stroke.
• The avatar is the existing ContactAvatar with the same ring. Not found uses the generic placeholder avatar.
• Type: name is textMedium, 2 lines then ellipsis. The handle is caption at 0.5, and the detail line is caption at 0.45. No new type tokens.
• Detail line: "Joined " comes from a new shared joinedLine(), which the profile screen now uses too, so the format lives in one place. It's omitted when joinedAt is null. Not found shows the existing "No Such Account" string in that spot, with the URL's @handle as the name.
• Loading is a 200×64 shimmer at the card radius.
• The card shares no code with the tip card. Its previews reuse the group card's previewPicture helper, which went from private to internal.

Stray punctuation (ChatListItem.splitAroundLinkCard)

• Punctuation touching the link goes with the link: link. and (link) give the card only, and link, then lunch gives the card then "then lunch". Punctuation after a space stays with its words. A leftover segment of only whitespace and punctuation is dropped, while symbols and emoji ($, 🎉) are kept. Copy still copies the original message.

Differences from iOS

• When a resolved profile has no display name and no username, iOS falls back to a generic counterpart name. Android has no equivalent string, so the name line is omitted and the handle/joined lines carry the card.

Also in this PR

• test(chat): ChatGroupCashLinkTest didn't compile on code/cash because ChatViewModel gained constructor dependencies. It now passes them, so the messenger tests run.