Introduce ColorStripSource as first-class entity

Extracts color processing and calibration out of WledPictureTarget into a
new PictureColorStripSource entity, enabling multiple LED targets to share
one capture/processing pipeline.

New entities & processing:
- storage/color_strip_source.py: ColorStripSource + PictureColorStripSource models
- storage/color_strip_store.py: JSON-backed CRUD store (prefix css_)
- core/processing/color_strip_stream.py: ColorStripStream ABC + PictureColorStripStream (runs border-extract → map → smooth → brightness/sat/gamma in background thread)
- core/processing/color_strip_stream_manager.py: ref-counted shared stream manager

Modified storage/processing:
- WledPictureTarget simplified to device_id + color_strip_source_id + standby_interval + state_check_interval
- Device model: calibration field removed
- WledTargetProcessor: acquires ColorStripStream from manager instead of running its own pipeline
- ProcessorManager: wires ColorStripStreamManager into TargetContext

API layer:
- New routes: GET/POST/PUT/DELETE /api/v1/color-strip-sources, PUT calibration/test
- Removed calibration endpoints from /devices
- Updated /picture-targets CRUD for new target structure

Frontend:
- New color-strips.js module with CSS editor modal and card rendering
- Calibration modal extended with CSS mode (css-id hidden field + device picker)
- targets.js: Color Strip Sources section added to LED tab; target editor/card updated
- app.js: imports and window globals for CSS + showCSSCalibration
- en.json / ru.json: color_strip.* and targets.section.color_strips keys added

Data migration runs at startup: existing WledPictureTargets are converted to
reference a new PictureColorStripSource created from their old settings.

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

server/src/wled_controller/storage/device_store.py

@@ -6,12 +6,6 @@ from datetime import datetime
 from pathlib import Path
 from typing import Dict, List, Optional, Tuple
 
-from wled_controller.core.capture.calibration import (
-    CalibrationConfig,
-    calibration_from_dict,
-    calibration_to_dict,
-    create_default_calibration,
-)
 from wled_controller.utils import get_logger
 
 logger = get_logger(__name__)
@@ -20,8 +14,9 @@ logger = get_logger(__name__)
 class Device:
     """Represents a WLED device configuration.
 
-    A device is a holder of connection state and calibration options.
-    Processing settings and picture source assignments live on PictureTargets.
+    A device holds connection state and output settings.
+    Calibration, processing settings, and picture source assignments
+    now live on ColorStripSource and WledPictureTarget respectively.
     """
 
     def __init__(
@@ -36,7 +31,6 @@ class Device:
         software_brightness: int = 255,
         auto_shutdown: bool = False,
         static_color: Optional[Tuple[int, int, int]] = None,
-        calibration: Optional[CalibrationConfig] = None,
         created_at: Optional[datetime] = None,
         updated_at: Optional[datetime] = None,
     ):
@@ -50,9 +44,10 @@ class Device:
         self.software_brightness = software_brightness
         self.auto_shutdown = auto_shutdown
         self.static_color = static_color
-        self.calibration = calibration or create_default_calibration(led_count)
         self.created_at = created_at or datetime.utcnow()
         self.updated_at = updated_at or datetime.utcnow()
+        # Preserved from old JSON for migration — not written back
+        self._legacy_calibration = None
 
     def to_dict(self) -> dict:
         """Convert device to dictionary."""
@@ -63,7 +58,6 @@ class Device:
             "led_count": self.led_count,
             "enabled": self.enabled,
             "device_type": self.device_type,
-            "calibration": calibration_to_dict(self.calibration),
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),
         }
@@ -81,20 +75,13 @@ class Device:
     def from_dict(cls, data: dict) -> "Device":
         """Create device from dictionary.
 
-        Backward-compatible: ignores legacy 'settings' and 'picture_source_id'
-        fields that have been migrated to PictureTarget.
+        Backward-compatible: reads legacy 'calibration' field and stores it
+        in _legacy_calibration for migration use only.
         """
-        calibration_data = data.get("calibration")
-        calibration = (
-            calibration_from_dict(calibration_data)
-            if calibration_data
-            else create_default_calibration(data["led_count"])
-        )
-
         static_color_raw = data.get("static_color")
         static_color = tuple(static_color_raw) if static_color_raw else None
 
-        return cls(
+        device = cls(
             device_id=data["id"],
             name=data["name"],
             url=data["url"],
@@ -105,11 +92,21 @@ class Device:
             software_brightness=data.get("software_brightness", 255),
             auto_shutdown=data.get("auto_shutdown", False),
             static_color=static_color,
-            calibration=calibration,
             created_at=datetime.fromisoformat(data.get("created_at", datetime.utcnow().isoformat())),
             updated_at=datetime.fromisoformat(data.get("updated_at", datetime.utcnow().isoformat())),
         )
 
+        # Preserve old calibration for migration (never written back by to_dict)
+        calibration_data = data.get("calibration")
+        if calibration_data:
+            try:
+                from wled_controller.core.capture.calibration import calibration_from_dict
+                device._legacy_calibration = calibration_from_dict(calibration_data)
+            except Exception:
+                pass
+
+        return device
+
 
 class DeviceStore:
     """Persistent storage for WLED devices."""
@@ -129,7 +126,7 @@ class DeviceStore:
     def load(self):
         """Load devices from storage file."""
         if not self.storage_file.exists():
-            logger.info(f"Storage file does not exist, starting with empty store")
+            logger.info("Storage file does not exist, starting with empty store")
             return
 
         try:
@@ -190,7 +187,6 @@ class DeviceStore:
         led_count: int,
         device_type: str = "wled",
         baud_rate: Optional[int] = None,
-        calibration: Optional[CalibrationConfig] = None,
         auto_shutdown: bool = False,
     ) -> Device:
         """Create a new device."""
@@ -203,7 +199,6 @@ class DeviceStore:
             led_count=led_count,
             device_type=device_type,
             baud_rate=baud_rate,
-            calibration=calibration,
             auto_shutdown=auto_shutdown,
         )
 
@@ -229,7 +224,6 @@ class DeviceStore:
         led_count: Optional[int] = None,
         enabled: Optional[bool] = None,
         baud_rate: Optional[int] = None,
-        calibration: Optional[CalibrationConfig] = None,
         auto_shutdown: Optional[bool] = None,
     ) -> Device:
         """Update device."""
@@ -249,13 +243,6 @@ class DeviceStore:
             device.baud_rate = baud_rate
         if auto_shutdown is not None:
             device.auto_shutdown = auto_shutdown
-        if calibration is not None:
-            if calibration.get_total_leds() != device.led_count:
-                raise ValueError(
-                    f"Calibration LED count ({calibration.get_total_leds()}) "
-                    f"does not match device LED count ({device.led_count})"
-                )
-            device.calibration = calibration
 
         device.updated_at = datetime.utcnow()
         self.save()