Add audio sources as first-class entities, add mapped CSS type, simplify target editor for mapped sources

- Audio sources moved to separate tab with dedicated CRUD API, store, and editor modal
- New "mapped" color strip source type: assigns different CSS sources to distinct LED sub-ranges (zones)
- Mapped stream runtime with per-zone sub-streams, auto-sizing, hot-update support
- Target editor auto-collapses segments UI when mapped CSS is selected
- Delete protection for CSS sources referenced by mapped zones
- Compact header/footer layout

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/storage/audio_source.py

@@ -0,0 +1,113 @@
+"""Audio source data model with inheritance-based source types.
+
+An AudioSource represents a reusable audio input configuration:
+  MultichannelAudioSource  — wraps a physical audio device (index + loopback flag)
+  MonoAudioSource          — extracts a single channel from a multichannel source
+"""
+
+from dataclasses import dataclass
+from datetime import datetime
+from typing import Optional
+
+
+@dataclass
+class AudioSource:
+    """Base class for audio source configurations."""
+
+    id: str
+    name: str
+    source_type: str  # "multichannel" | "mono"
+    created_at: datetime
+    updated_at: datetime
+    description: Optional[str] = None
+
+    def to_dict(self) -> dict:
+        """Convert source to dictionary. Subclasses extend this."""
+        return {
+            "id": self.id,
+            "name": self.name,
+            "source_type": self.source_type,
+            "created_at": self.created_at.isoformat(),
+            "updated_at": self.updated_at.isoformat(),
+            "description": self.description,
+            # Subclass fields default to None for forward compat
+            "device_index": None,
+            "is_loopback": None,
+            "audio_source_id": None,
+            "channel": None,
+        }
+
+    @staticmethod
+    def from_dict(data: dict) -> "AudioSource":
+        """Factory: dispatch to the correct subclass based on source_type."""
+        source_type: str = data.get("source_type", "multichannel") or "multichannel"
+        sid: str = data["id"]
+        name: str = data["name"]
+        description: str | None = data.get("description")
+
+        raw_created = data.get("created_at")
+        created_at: datetime = (
+            datetime.fromisoformat(raw_created)
+            if isinstance(raw_created, str)
+            else raw_created if isinstance(raw_created, datetime)
+            else datetime.utcnow()
+        )
+        raw_updated = data.get("updated_at")
+        updated_at: datetime = (
+            datetime.fromisoformat(raw_updated)
+            if isinstance(raw_updated, str)
+            else raw_updated if isinstance(raw_updated, datetime)
+            else datetime.utcnow()
+        )
+
+        if source_type == "mono":
+            return MonoAudioSource(
+                id=sid, name=name, source_type="mono",
+                created_at=created_at, updated_at=updated_at, description=description,
+                audio_source_id=data.get("audio_source_id") or "",
+                channel=data.get("channel") or "mono",
+            )
+
+        # Default: multichannel
+        return MultichannelAudioSource(
+            id=sid, name=name, source_type="multichannel",
+            created_at=created_at, updated_at=updated_at, description=description,
+            device_index=int(data.get("device_index", -1)),
+            is_loopback=bool(data.get("is_loopback", True)),
+        )
+
+
+@dataclass
+class MultichannelAudioSource(AudioSource):
+    """Audio source wrapping a physical audio device.
+
+    Captures all channels from the device.  For WASAPI loopback devices
+    (system audio output), set is_loopback=True.
+    """
+
+    device_index: int = -1      # -1 = default device
+    is_loopback: bool = True    # True = WASAPI loopback (system audio)
+
+    def to_dict(self) -> dict:
+        d = super().to_dict()
+        d["device_index"] = self.device_index
+        d["is_loopback"] = self.is_loopback
+        return d
+
+
+@dataclass
+class MonoAudioSource(AudioSource):
+    """Audio source that extracts a single channel from a multichannel source.
+
+    References a MultichannelAudioSource and selects which channel to use:
+    mono (L+R mix), left, or right.
+    """
+
+    audio_source_id: str = ""   # references a MultichannelAudioSource
+    channel: str = "mono"       # mono | left | right
+
+    def to_dict(self) -> dict:
+        d = super().to_dict()
+        d["audio_source_id"] = self.audio_source_id
+        d["channel"] = self.channel
+        return d