Refactor screen recorder to single-process architecture, add a control panel and new settings

[fliplus]

Summary

Recording and replay buffer now share a single process instead of two separate process trees. State is driven by actual process events rather than timers. A new panel and several settings were added.

New Features

• Panel widget: control panel with start/stop recording and replay buttons, plus a recording timer
• Button action setting: bar and control center widgets now have a configurable click action: toggle recording, toggle replay, save replay, or open panel
• Rate control setting: QP, VBR, or CBR. When CBR is selected, a bitrate field (kbps) replaces the quality preset
• Post-recording script: path to a script to run after each recording/replay saves
• Replay notifications toggle and auto-start replay on plugin load

Changes

• Replaced the dual recording/replay process architecture with a single recorderProcess shared by both modes (recording and replaying); all replay-specific processes were removed
• Removed isPending, isReplayPending, hasActiveRecording and all associated timers; state is now two booleans (isRecording, isReplaying) driven directly by process events
• Backend detection (native vs. flatpak) moved from plugin startup to recording start via a dedicated backendCheckProcess; the startup checker process and isAvailable state removed
• Starting a recording while replay is active now reuses the existing portal session (sends SIGRTMIN) instead of launching a new process
• Filename pattern is now fixed as Video_yyyy-MM-dd_HH-mm-ss.mp4; the user-configurable filenamePattern setting was removed. This was done for consistency with replay mode, which does not support custom file names
• IPC handlers renamed: toggle -> toggleRecording, start -> startRecording, stop -> stopRecording
• Removed replayEnabled setting, replay is always available
• Settings menu reordered and reorganised into General / Video / Audio / Replay sections
• General code cleanup and refactoring throughout the whole plugin
• Version bumped 1.3.7 -> 1.4.0

Notes: I have only tested this on NixOS with Niri and the native gpu-screen-recorder package. Flatpak and Hyprland have not been tested. Non-English translations were generated with AI, I cannot guarantee they are accurate.

[github-actions]

@Ly-sec - this PR modifies your plugin. Please review when you have a chance.

[github-actions]

Automatic Code Quality Review

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File: screen-recorder/BarWidget.qml

• (H) Missing required property widgetId. For example:

property string widgetId: ""

• (H) Missing required property section. For example:

property string section: ""

• (H) Missing required property sectionWidgetIndex. For example:

property int sectionWidgetIndex: -1

• (H) Missing required property sectionWidgetsCount. For example:

property int sectionWidgetsCount: 0