Add world.searchObjects RPC with volume support

[YoloWingPixie]

Expose DCS’ world.searchObjects via WorldService/SearchObjects with full volume support (sphere, box, segment, pyramid).

• Proto: define SearchObjectsRequest with SearchVolume (sphere/box/ segment/pyramid) using InputPosition for geo points; response returns dcs.common.v0.Target[] to reuse the existing union object type
• Lua: implement GRPC.methods.searchObjects; build DCS volume tables (world.VolumeType.*) and flattened shapes; return objects wrapped in Target oneof
• Rust: wire WorldService::search_objects to Lua method

Example request payload:

{
  "categories": [1],
  "volume": {
    "sphere": {
      "center": { "lat": 41.9, "lon": 41.9, "alt": 200 },
      "radius": 3000000
    }
  }
}

Example request payload for a pyramid search:

{
  "categories": [1],
  "volume": {
    "pyramid": {
      "center": { "lat": 43.0, "lon": 44.0, "alt": 0 },
      "forward": { "x": 1, "y": 0, "z": 0 },
      "right":   { "x": 0, "y": 0, "z": 1 },
      "up":      { "x": 0, "y": 1, "z": 0 },
      "length": 3000000,
      "halfAngleHorizontal": 1.56,
      "halfAngleVertical": 1.56
    }
  }
}

Example response:

{
  "objects": [
    {
      "unit": {
        "id": 2,
        "name": "Aerial-2-1",
        "callsign": "Springfield11",
        "coalition": "COALITION_BLUE",
        "type": "A-10A",
        "position": {
          "lat": 43.80128964094778,
          "lon": 36.80316924193918,
          "alt": 1962.2799072265625,
          "u": 206424.18943715096,
          "v": -141278.69705298543
        },
        "orientation": {
          "heading": 95.71059450833623,
          "yaw": 98.36883403042783,
          "pitch": 7.451955739887493,
          "roll": 0.0000330837287922511,
          "forward": {
            "x": -0.098663330078125,
            "y": 0.12969478964805603,
            "z": 0.9866330623626709
          },
          "right": {
            "x": -0.9950371980667114,
            "y": -5.774199962615967e-7,
            "z": -0.09950366616249084
          },
          "up": {
            "x": 0.012904536910355091,
            "y": 0.9915539622306824,
            "z": -0.12905119359493256
          }
        },
        "velocity": {
          "heading": 95.7105901371753,
          "speed": 123.22611009175196,
          "velocity": {
            "x": -12.261449813842773,
            "y": 1.445429801940918,
            "z": 122.61456298828125
          }
        },
        "group": {
          "id": 2,
          "name": "Aerial-2",
          "coalition": "COALITION_BLUE",
          "category": "GROUP_CATEGORY_AIRPLANE"
        },
        "number_in_group": 1
      }
    },
    {
      "unit": {
        "id": 8,
        "name": "Ground-3-1",
        "callsign": "",
        "coalition": "COALITION_BLUE",
        "type": "mrap_mk19",
        "position": {
          "lat": 45.0422479049929,
          "lon": 38.10749053330819,
          "alt": 5.001004695892334,
          "u": 302734.90625,
          "v": 2232.5100098262274
        },
        "orientation": {
          "heading": 0,
          "yaw": 3.6502970123791134,
          "pitch": 0,
          "roll": 0,
          "forward": {
            "x": 1,
            "y": 0,
            "z": 0
          },
          "right": {
            "x": 0,
            "y": 0,
            "z": 1
          },
          "up": {
            "x": 0,
            "y": 1,
            "z": 0
          }
        },
        "velocity": {
          "heading": 0,
          "speed": 0,
          "velocity": {
            "x": 0,
            "y": 0,
            "z": 0
          }
        },
        "group": {
          "id": 8,
          "name": "Ground-3",
          "coalition": "COALITION_BLUE",
          "category": "GROUP_CATEGORY_GROUND"
        },
        "number_in_group": 1
      }
    }
  ]
}