Improve camera preview scaling, overlay templates, and gallery/locations UI

[krishna3554]

Motivation

• Fix the camera preview letterboxing so the live feed fills the screen edge-to-edge while preserving camera controller initialization and capture resolution.
• Make the on-camera and burned-in location overlays more legible and visually distinct without touching backend location or saving logic.
• Replace the bottom-bar Settings entry with a persistent Templates picker and provide three overlay styles (Classic Dark, Minimal Strip, Field Report) that update live.
• Improve the Locations and Gallery screens for clearer hierarchy, grouping, and interactivity while keeping existing app functionality intact.

Description

• Camera preview scaling: added _CameraPreviewCover and use of the controller previewSize with FittedBox(fit: BoxFit.cover) so the preview fills the viewport exactly without changing CameraController initialization; changes in lib/features/camera/screen/camera_screen.dart.
• Overlay templates and UI: added persistent overlayTemplate to AppSettings and SettingsService, implemented a Templates bottom sheet (_showTemplateSheet and _TemplateChoiceTile) and removed the bottom-bar Settings entry in lib/features/camera/screen/camera_screen.dart and lib/models/app_settings.dart / lib/services/settings_service.dart.
• Overlay readability and stamping: refactored LocationStampCard to support three templates, improved typography, spacing, contrast, compact preview, and map thumbnail clipping in lib/core/widgets/location_stamp_card.dart, and made ImageOverlayService apply the selected template when composing burned-in images and added rendering code for minimal_strip and field_report in lib/services/image_overlay_service.dart.
• Locations screen redesign: added search, date grouping, card-style rows with map thumbnail and photo count badges, expandable thumbnails, long-press actions, and a map toggle in lib/features/locations/screen/locations_screen.dart.
• Gallery improvements: converted to date-grouped Sliver sections, tighter 3-column grid, thumbnail overlays, selection mode with share/delete, and a swipeable/pinch-zoom full-screen viewer with share/info/delete controls in lib/features/gallery/screen/gallery_screen.dart.
• Result saving: pass selected template through to the image composer so live-template selection matches the final saved photo in lib/features/result/screen/result_screen.dart and lib/services/image_overlay_service.dart.

Files changed (high level): lib/features/camera/screen/camera_screen.dart, lib/core/widgets/location_stamp_card.dart, lib/services/image_overlay_service.dart, lib/models/app_settings.dart, lib/services/settings_service.dart, lib/features/locations/screen/locations_screen.dart, lib/features/gallery/screen/gallery_screen.dart, lib/features/result/screen/result_screen.dart.

Testing

• Ran git diff --check to verify there are no whitespace/indexing issues and it passed.
• Attempted to run dart format and flutter analyze (dart format ... && flutter analyze) but the environment does not have dart/flutter installed so automatic formatting and static analysis could not be executed.
• Attempted flutter test but the environment does not have flutter installed so unit/widget tests could not be executed here.

---

Codex Task