feat: Add 'call' support to improve 2-way audio experience (#2486)

Draws significant inspiration (and direct styling) from
https://github.com/dermotduffy/advanced-camera-card/pull/2447 . Thank
you @Maudfer !

BREAKING CHANGE:

The microphone condition previously bundled two unrelated signals —
whether a two-way-audio session was connected and whether the microphone
was muted. Connection state is now its own dedicated call condition, and
microphone is reserved purely for mute state. Configs are upgraded
automatically (the card rewrites affected conditions under overrides,
elements, and automations). If you maintain config by hand, convert as
follows:

If you only used connected:

# Before
```yaml
condition: microphone
connected: true
```

# After
```yaml
condition: call
call: true
```
If you used both connected and muted — they must be split into two
conditions, since they no longer live together:

# Before
```yaml
condition: microphone
connected: true
muted: false
```

# After
```yaml
condition: and
conditions:
  - condition: call
    call: true
  - condition: microphone
    muted: false
```

docs/configuration/media-viewer.md

@@ -50,10 +50,11 @@ media_viewer:
       # [...]
 ```
 
-| Option  | Default      | Description                                                                                                                                      |
-| ------- | ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------ |
-| `size`  | `48`         | The size of the next/previous controls in pixels. Must be >= `20`.                                                                            |
-| `style` | `thumbnails` | When viewing media, what kind of controls to show to move to the previous/next media item. Acceptable values: `thumbnails`, `chevrons`, `none` . |
+| Option      | Default      | Description                                                                                                                                        |
+| ----------- | ------------ | -------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `auto_hide` | `[casting]`  | The conditions under which the next/previous controls auto-hide. The only condition is `casting` (the card is being cast). Set to `[]` to disable. |
+| `size`      | `48`         | The size of the next/previous controls in pixels. Must be >= `20`.                                                                              |
+| `style`     | `thumbnails` | When viewing media, what kind of controls to show to move to the previous/next media item. Acceptable values: `thumbnails`, `chevrons`, `none` .   |
 
 ### `ptz`
 
@@ -183,6 +184,8 @@ media_viewer:
   controls:
     builtin: true
     next_previous:
+      auto_hide:
+        - casting
       size: 48
       style: thumbnails
     wheel: true