feat(ui): add Welcome screen scaffold (no navigation)

[ilmoniemi]

User Story

As a new user opening Pyrycode Mobile for the first time, I want a welcoming landing screen that tells me what the app is and offers a clear next step (either pair with an existing pyrycode CLI or set one up), so I'm not dropped into a blank app with no context.

Context

This is the first onboarding-flow ticket. The screen is built as a pure Composable taking navigation callbacks; the actual routing (NavHost in #8) and destination wiring (Scanner + external browser in #14) land in follow-up tickets. The visual reference is Figma node 6:32 (412×892 baseline).

#8 will render this screen at the welcome route (or a placeholder if #7 hasn't merged yet), and #14 will pass real callbacks for the two CTAs. Keeping this ticket free of NavController / Intent code is what makes that parallel work clean.

Acceptance Criteria

• A stateless Composable lives in ui/onboarding/ named WelcomeScreen, with signature @Composable fun WelcomeScreen(onPaired: () -> Unit, onSetup: () -> Unit) (signature is fixed because feat(ui): set up Navigation Compose with Welcome → ChannelList placeholder #8 and feat(ui): wire Welcome screen CTAs to Scanner navigation + external browser #14 consume it).
• Layout matches Figma 6:32 at the 412×892 baseline: hero section (logo placeholder, "Pyrycode Mobile" title, subtitle), primary CTA "I already have pyrycode" invoking onPaired, secondary CTA "Set up pyrycode first" invoking onSetup, open-source footer line at the bottom.
• Colors and typography come from MaterialTheme.colorScheme.* and MaterialTheme.typography.* only — no hardcoded Color(0x...) literals or hardcoded font sizes / weights / families.
• No NavController import or reference anywhere in the file — navigation is invoked through the two callback parameters only.
• Two @Preview composables render the screen, one with light scheme and one with dark scheme (uiMode = UI_MODE_NIGHT_YES), both wrapped in the app's MaterialTheme.
• ./gradlew assembleDebug passes.

Technical Notes

• Pure stateless Composable; no ViewModel, no remember-based state needed for this ticket.
• Use a placeholder for the logo (e.g. a sized Box with colorScheme.primary or Icon with a stock vector) — the real logo asset is not part of this ticket.
• The Figma export's React+Tailwind output is a reference, not literal: adapt to Compose + Material 3 conventions.

Out of Scope

• NavHost / NavController wiring (feat(ui): set up Navigation Compose with Welcome → ChannelList placeholder #8)
• Real CTA destinations — Scanner route and external browser intent (feat(ui): wire Welcome screen CTAs to Scanner navigation + external browser #14)
• Real logo / branding asset import
• Conditional start destination based on pairing state (feat(ui): conditional NavHost start destination based on paired-server-exists #13)

Depends On

None — runs in parallel with the data-layer chain. #8 and #14 depend on this.

Size Estimate

S — single stateless Composable file with layout tree + two preview composables; <100 LOC, no logic.

[ilmoniemi]

🤖 Product Owner — creates structured issues

po agent has completed work on this ticket.

Agent output (click to expand)

Refined #7 to the standard PO format and bumped size:xs → size:s.

**Changes:**
- Reframed Goal into User Story + Context, calling out the relationship to #8 (NavHost) and #14 (CTA wiring) so the architect sees why this is deliberately callback-only.
- Tightened acceptance criteria to be testable / mechanically checkable (signature fixed, no `NavController` import, no hardcoded color/typography literals, two `@Preview` composables with explicit `uiMode`).
- Added Technical Notes flagging the logo as a placeholder and reminding that the Figma React+Tailwind output is a reference, not literal output.
- **Size bumped XS → S.** A hero + 2 CTAs + footer + 2 previews realistically lands ≥30 LOC of layout markup; XS is "<30 LOC trivial change". Architect can override S → XS later if they disagree.
- **No `security-sensitive` label** — pure UI scaffold, no input/network/crypto.

No split needed: passes the one-sentence test ("Add a stateless Welcome screen Composable matching Figma 6:32 with hero, two CTAs, and a footer") — the "and" joins content within a single screen, not separate concerns. No comment was added since there was no specific rework reason to address.

Ready for human review. Move to the next column when approved.

[ilmoniemi]

🤖 System Architect — defines Go interfaces, data flows, concurrency patterns

architect agent has completed work on this ticket.

Agent output (click to expand)

Spec written and committed at `docs/specs/architecture/7-welcome-screen-scaffold.md`. Key decisions:

- **One file**, `app/src/main/java/de/pyryco/mobile/ui/onboarding/WelcomeScreen.kt`, signature locked to `WelcomeScreen(onPaired, onSetup)` per AC1.
- **Layout**: `Surface` → `Column(SpaceBetween, CenterHorizontally)` with hero (centered logo `Box` + title `displaySmall` + subtitle `bodyLarge`), CTA stack (`Button` primary, `OutlinedButton` secondary, both `fillMaxWidth`), and footer (`bodySmall`).
- **Tokens only**: all colors via `MaterialTheme.colorScheme.*`, all type via `MaterialTheme.typography.*`. Spacing dp values are layout, not banned by AC3.
- **Logo placeholder**: defaulted to a plain `Box(primaryContainer)` with no inner icon to keep the file dependency-free (no `material-icons-extended` in `libs.versions.toml`).
- **Previews**: two `@Preview`s, light + dark, both at 412×892 with explicit `darkTheme = false/true`, wrapped in `PyrycodeMobileTheme`, marked `private`.
- **Out of scope**: NavController, Intent, ViewModel, tests beyond `assembleDebug`.

Ready for human review. Move to the next column when approved.