Home as drafts hub, camera close UX, light/dark mode, upload destination

[morepriyam]

Closes #275 (Refactor welcome screen – plus = new pulse, welcome = list of drafts)
Closes #209 (Enhance landing page – show drafts on main page, option to make new one)

https://youtube.com/shorts/D43Z9nYwx2s?si=D_t72uLUvwaSa6xx

Summary

• Home is the single place for all drafts: list, open, import, export. Shorts/Drafts navigation removed from camera.
• + button always opens camera with a new draft (no auto-load of last draft).
• Close on camera/shorts is a single action (no Start New / Start Over / Close menu). In upload mode, close goes to home (tabs) so users don’t land on a white screen after a QR deeplink.
• Home supports light/dark mode and shows upload destination (full server URL) for upload drafts. Export is shown only when there are drafts.

Changes

Navigation & layout

• app/(camera)/_layout.tsx: Remove Shorts/Drafts bottom nav; camera stack only shows shorts screen.
• app/(camera)/drafts.tsx: Removed; drafts list and import/export live on home.

Draft behavior

• hooks/useDraftManager.ts: When draftId is not passed, do not load last modified draft; start with an empty draft and no redo stack. QR/deeplink flow (with draftId) unchanged.

Close button

• components/CloseButton.tsx, components/UploadCloseButton.tsx: Single close action only (onClose); no modal with Start New / Start Over / Close.
• app/(camera)/shorts.tsx: Close runs handleClose() then, in upload mode, router.replace("/(tabs)") (avoids white screen after QR); in camera mode, router.back().

Home (tabs/index)

• app/(tabs)/index.tsx: Full drafts list, Import, Export (only when drafts exist), open draft → camera/shorts with draftId and mode. Light/dark theme via Colors (surface, border, secondaryText, selection, inputBackground). Delete uses MaterialIcons delete-outline. Upload drafts show link icon + full server URL below segment/timestamp. Export button only when drafts.length > 0.
• constants/Colors.ts: Add surface, border, secondaryText, inputBackground, selection for light and dark.

Testing

• Open app → home shows drafts (or empty state). Tap + → camera with new draft. Close → back to home.
• Tap a draft on home → shorts opens with that draft. Close → back to home.
• Scan QR (upload deeplink) → shorts opens with draft. Close → home (no white screen).
• Toggle device light/dark → home and draft list follow theme.
• With no drafts, only Import is shown; with drafts, Export appears.