feat(media): add media volume osd with media player name

[AdityaKr015]

Summary

This PR shows OSD when media volume is changed with playerctl, with MPRIS supported Media Player Name with disc-filled icon.

Motivation

For the people who wants OSD when changing media volume.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Build / packaging

Related Issue

Closes #3791

Testing

• Ran just format,`meson compile -C build-debug no issue.
• Ran meson test -C build-debug all 72 tests passed.
• Then just lint all clear no errors.
• Killed the current running noctalia pkill noctalia then started new feature one ./build-debug/noctalia
• Then tested manually using playerctl cmd using VLC, Celluloid, Dragon Player, Elisa

Manual Coverage

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Tested with different bar positions and density settings
• Tested at different interface scaling values
• Tested with multiple monitors

Screenshots / Videos

I have tested with celluloid, elisa, dragon player. All of them works, just did took screenshot for them

Checklist

• This PR is ready for review
• I read and followed the relevant guidance in CONTRIBUTING.md.
• I ran just format with clang-format v22+ installed
• I ran the relevant build or test commands
• I self-reviewed the changes.
• I checked for new warnings or errors.
• I will update end-user documentation after merge, or this PR does not change user-facing configuration or behavior.
• I added or updated assets/translations/en.json, or this PR adds no new user-facing strings.
• I did not edit non-English translation files unless this PR is explicitly for translation tooling, an import/export sync, or a maintainer-requested locale change.
• I used the existing canonical names for config keys, IPC names, paths, and identifiers.

[ItsLemmy]

[P2] Preserve the debounce window for trailing property refreshes — src/dbus/mpris/mpris_service.cpp:1658-1667

DeferredCall::callLater() runs at the next main-loop iteration, not after the remaining 120 ms debounce interval. The
callback also removes busName from m_pendingPropertiesRefresh before dispatching addOrRefreshPlayer().

Consequently, a player emitting PropertiesChanged every 16 ms can still trigger a two-interface GetAll refresh on every loop iteration; the existing debounce is effectively bypassed. Schedule one trailing refresh for the end of
kPropertiesDebounceWindow, keeping it pending until that timer fires. A source-level simulation of 11 signals at 16 ms
intervals produced 11 refreshes rather than approximately two.

[P2] Reset the volume baseline when the active player changes — src/shell/osd/media_osd.cpp:55-56

m_lastVolumeis global to MediaOsd and is compared without checking activePlayer.busName. Active-player selection
itself invokes the MPRIS change callback. Switching from paused player A at 30% to paused player B at 80%, without
changing either volume, therefore sets trackChanged == false and volumeChanged == true, displaying a false “B — 80%” volume OSD. Track the baseline per bus name, or reseed m_lastVolume whenever the active bus name changes.