General: Refresh Play Store screenshots and add Watcher screen

[d4rken]

What changed

Refreshed the Play Store / GitHub README screenshots:

• The screenshot set now includes the Permission Watcher dashboard (showing app installs, updates, removals, and permission changes — one of the headline features that was previously absent from the screenshots).
• Dropped the duplicate dark-mode Overview screenshot and the Settings screenshot — both added little to the store listing.
• The shipped en-US screenshots are regenerated from a corrected layout that matches what users actually see in production (the wrapper used in the screenshot pipeline previously rendered the bottom navigation bar covering content, and was missing the Watcher tab entirely).
• README image grid trimmed from 10 broken/stale references to 6 properly-named screenshots, switched to relative paths so previews render correctly in PR diffs as well as on the rendered README.

Technical Context

• WatcherDashboardPreviewData (new): 5 reports covering all four WatcherEventType values (UPDATE, INSTALL, GRANT_CHANGE, REMOVED) with realistic app names lifted from AppsPreviewData for cross-screenshot consistency. Uses fixed epoch-millis timestamps (no System.currentTimeMillis()) so screenshot regenerations are deterministic instead of churning every run.
• WatcherDashboardScreen inline preview now reuses the new shared WatcherDashboardPreviewData.loadedState() instead of duplicating its own state — single source of truth between IDE preview and Play Store screenshot.
• ScreenshotContent.WithBottomBar rewritten from Box overlay to Column { Box(weight=1f) { content }; NavigationBar { … } } matching the production MainScreen layout. Previously the bar was overlaid on top of the content (would cover the Watcher FAB and bottom rows of lists). Also bumped from 3 to 4 tabs to match production, with a sample Badge { Text("3") } on the Watcher tab so the shipped screenshots reflect the real bottom bar users see.
• Pipeline scripts: dropped the now-dead @PlayStoreLocalesDark annotation class and its generator block in generate_screenshots.sh. Updated composable count from 7 to 6. Added a BATCH_SIZE_EXPLICIT flag so --smoke --batch-size N actually honors the override — without it, smoke mode forces all 6 locales into a single batch and PermissionDetails OOMs in layoutlib.
• copy_screenshots.sh SCREEN_MAP rebuilt for the new 6-entry screen set.
• Stale 2022 screenshot1.png … screenshot10.png files removed from en-US. The en-US directory plus the 5 smoke-incidental locales (de-DE, ja-JP, ar, zh-CN, pt-BR) now contain the new descriptive PNGs (1_overview_light.png through 6_watcher.png). Other 33 locales still hold no screenshots — full multi-locale regeneration is left for a separate ~20-minute run.

Review guidance

• Visual: the 6 new en-US PNGs in fastlane/metadata/android/en-US/images/phoneScreenshots/ are the easiest way to sanity-check the output.
• The WithBottomBar rewrite affects every existing tab screenshot (Overview/Apps/Permissions) — they all now show the corrected 4-tab bar with the Watcher badge, so binary diffs there are expected.