Add torrent streamer, UI overhaul, switch to GPL

Major updates: adds a libtorrent-based streaming service and refactors UI/behaviour.

Key changes:
- Add streaming service (src/kadr/services/streamer.py): HTTP server + sequential download streamer using libtorrent, StreamLog, buffering/ready states and local streaming URL.
- Rework Detail view (src/kadr/views/detail.py): new hero/backdrop layout, poster sizing, metadata chips, tagline, overview, cast placeholder and a "Watch" action that navigates to a Torrents view; loads full TMDB details/credits asynchronously.
- UI styling (src/kadr/data/style.css): many new classes for detail/hero/cast styling.
- Downloads manager improvements (src/kadr/services/downloads.py): temp dir for torrents, cleanup of stale files, history size cap, unified client launch with error handling.
- TMDB client refactor (src/kadr/services/tmdb.py): unified _fetch helper, added movie_credits/tv_credits endpoints.
- Utils improvements (src/kadr/utils.py): thread-safe LRU image cache, image download concurrency, and slight clipboard command ordering tweak.
- Jackett servers list updated (src/kadr/services/jackett.py): reorder/add servers.
- Project metadata & licensing: switch LICENSE to GPL-3.0-or-later, update pyproject.toml and application about dialog to GPL, adjust package/version in pyproject and __init__.
- README revamped (README.md): reorganized, added badges, Russian text, install/usage sections.
- Added new view/widget files (player/torrents/mpv_widget) and other UI tweaks across widgets/window.

These changes add streaming playback capability, tighten resource handling, and refresh the detail UI while changing the project license to GPL-3.0-or-later.

LICENSE

@@ -1,21 +1,39 @@
-MIT License
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
 
-Copyright (c) 2026 Cheviiot (https://github.com/Cheviiot)
+ Copyright (C) 2026 Cheviiot
 
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
 
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+
+                    DETAILED TERMS AND CONDITIONS
+
+  0. Definitions.
+
+  "This License" refers to version 3 of the GNU General Public License.
+
+  "The Program" refers to any copyrightable work licensed under this
+ License. Each licensee is addressed as "you". "Licensees" and
+ "recipients" may be individuals or organizations.
+
+  To "modify" a work means to copy from or adapt all or part of the work
+ in a fashion requiring copyright permission, other than the making of an
+ exact copy. The resulting work is called a "modified version" of the
+ earlier work or a work "based on" the earlier work.
+
+  A "covered work" means either the unmodified Program or a work based
+ on the Program.
+
+  The full text of the GNU General Public License version 3 is available at:
+  <https://www.gnu.org/licenses/gpl-3.0.txt>