Modernize app structure, migrations, admin tooling, and media workflows

Summary

This is a large modernization pass across the app, database, admin tooling, media workflows, and frontend behavior.

It is not a narrow feature branch. In practice this MR:

• finishes a broad move toward the newer app/ structure
• removes a lot of legacy root-level duplication and wrapper logic
• introduces real DB migrations/versioning
• adds maintenance/admin tooling for schema and media operations
• refactors upload/media behavior into shared helpers/services
• expands JS/UI behavior on mobile, upload, settings, profile, users, and menu flows
• adds Shaka configuration/admin controls
• adds the first end-to-end backend plumbing for admin-only yt-dlp video URL imports

Major changes

App structure / legacy cleanup

• moved more behavior behind the newer app/ route/controller/lib layout
• thinned legacy entrypoints and kept compatibility wrappers where needed
• removed a large amount of older duplicated inline/root-level behavior
• consolidated more shared logic into library helpers and service-style modules

Database versioning and schema work

• added real database migration infrastructure and app version tracking
• added migration status/apply tooling and admin visibility for migration history
• introduced schema changes through migrations instead of ad hoc DB drift
• normalized the live schema toward utf8mb4
• added index migrations for common query patterns
• added a video_imports table for yt-dlp/source-import metadata
• added comment soft-delete support
• moved profile data directionally toward users instead of profils

Admin panel

• switched admin auth to DB-backed users.priv = 1
• removed the older config-based admin identity split
• added/expanded:
  • Maintenance tab
  • Shaka tab
  • migration history visibility
  • DB backup download
  • bulk thumbnail regeneration
  • video metadata backfill controls
  • config editing improvements
• reordered and cleaned parts of the admin navigation and config experience

Media / upload / lifecycle

• refactored upload logic toward shared pipeline/repository helpers
• unified more of image/video processing and metadata persistence
• added shared media path/lifecycle handling for more routes
• added video metadata upsert behavior and admin refresh/backfill paths
• added admin-only yt-dlp import plumbing on the video upload page:
  • format probe
  • video/audio stream selection
  • staged temp download
  • handoff into the existing upload pipeline
  • persistence of source/import metadata in video_imports

Player / Shaka

• kept Shaka rather than switching players
• moved Shaka asset URLs/version into config
• added a dedicated admin surface for Shaka settings
• switched the player wrapper to a local script while keeping Shaka assets configurable by URL

Frontend / JS / mobile

• modernized the mobile media list flow
• added mobile auto-detection for routes that already had mobile views
• improved upload UX:
  • file removal
  • reorder before upload
  • paste-from-clipboard for images
  • unload warning during active upload
  • richer success states
• improved viewer UX:
  • overlay close behavior
  • copy-link toast
  • video keyboard shortcuts
• improved settings/profile/users/menu JS behavior
• added a JS test harness and coverage for the newer frontend modules

Migrations included

This MR includes the migration chain up through:

• comments soft delete
• video metadata schema work
• users/profils backfill direction
• common index additions
• schema migration metadata sync
• video_imports
• utf8mb4 normalization

Config / environment notes

• includes config.local.php
• does not include config.dev.php
• yt-dlp import is feature-gated and disabled by default
• yt-dlp import also depends on a working yt-dlp binary/path in the target environment
• Shaka asset URLs and version are now config-driven

Verification run

Ran:

• php tests/run.php
• npm run test:js
• php tests/admin_smoke_runner.php overview
• php tests/admin_smoke_runner.php config
• php tests/admin_smoke_runner.php maintenance
• php tests/admin_smoke_runner.php database
• php tests/admin_smoke_runner.php system
• php tests/admin_smoke_runner.php shaka

Known gaps / honest notes

• yt-dlp import plumbing is implemented, but this environment did not have yt-dlp available on PATH, so a real live import against YouTube was not exercised here
• non-English locale files were not fully hand-translated for every new string; English fallback covers the new keys
• the older animehu.hu sidecar/orphan endpoints were intentionally left alone
• this is a broad refactor, so review should assume meaningful risk even though tests are green
• mobile UI still deserves a dedicated real-browser QA pass, especially around the custom mobile shell/drawer behavior

Reviewer notes

This MR is easiest to review by subsystem, not file-by-file in raw diff order:

1. migrations / schema / admin auth
2. admin panel + maintenance/config/shaka tabs
3. upload/media pipeline and repository changes
4. yt-dlp import plumbing
5. frontend/mobile/upload/menu/settings JS work
6. legacy wrapper cleanup / route consolidation