feat: initial CamWatch service

Polls Frigate events API, extracts dominant vehicle color (KMeans),
reads LPR plate from Frigate sub_label. Responsive dark UI with
filter by plate/camera/date and auto-refresh. FastAPI + SQLite.

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

app/analyzer.py

@@ -0,0 +1,60 @@
+import cv2
+import numpy as np
+import colorsys
+
+
+def extract_dominant_color(image_path: str, bbox: dict | None = None) -> tuple[str, str]:
+    """Returns (hex_color, color_name) from image, optionally cropped to bbox."""
+    img = cv2.imread(image_path)
+    if img is None:
+        return "#808080", "Inconnu"
+
+    if bbox:
+        h, w = img.shape[:2]
+        x1 = max(0, int(bbox.get("x", 0) * w))
+        y1 = max(0, int(bbox.get("y", 0) * h))
+        x2 = min(w, int((bbox.get("x", 0) + bbox.get("width", 1)) * w))
+        y2 = min(h, int((bbox.get("y", 0) + bbox.get("height", 1)) * h))
+        if x2 > x1 and y2 > y1:
+            img = img[y1:y2, x1:x2]
+
+    small = cv2.resize(img, (60, 60), interpolation=cv2.INTER_AREA)
+    pixels = small.reshape(-1, 3).astype(np.float32)
+
+    k = min(4, len(pixels))
+    _, labels, centers = cv2.kmeans(
+        pixels, k, None,
+        (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 20, 1.0),
+        10, cv2.KMEANS_RANDOM_CENTERS
+    )
+    counts = np.bincount(labels.flatten())
+    dominant = centers[np.argmax(counts)]
+    b, g, r = int(dominant[0]), int(dominant[1]), int(dominant[2])
+    hex_color = f"#{r:02x}{g:02x}{b:02x}"
+    return hex_color, _name_color(r, g, b)
+
+
+def _name_color(r: int, g: int, b: int) -> str:
+    h, s, v = colorsys.rgb_to_hsv(r / 255, g / 255, b / 255)
+    if v < 0.18:
+        return "Noir"
+    if v > 0.82 and s < 0.18:
+        return "Blanc"
+    if s < 0.18:
+        return "Gris"
+    hue = h * 360
+    if hue < 15 or hue >= 345:
+        return "Rouge"
+    if hue < 45:
+        return "Orange"
+    if hue < 75:
+        return "Jaune"
+    if hue < 150:
+        return "Vert"
+    if hue < 195:
+        return "Cyan"
+    if hue < 255:
+        return "Bleu"
+    if hue < 290:
+        return "Violet"
+    return "Rose"