Move Odin renderer into gui/ with per-project Makefiles

Each sub-project (gui, api, infra) now owns its own Makefile, and the
root Makefile is a lean delegator for the base commands (run, build,
test, clean, fmt). Odin source, deps, and web assets live under gui/
(gui/src, gui/lib, gui/www), with scripts kept under gui/scripts for
build tooling only.

gui/src/main.odin

@@ -0,0 +1,113 @@
+package main
+
+import "core:math"
+import "core:math/rand"
+import rl "vendor:raylib"
+
+WIDTH :: 1280
+HEIGHT :: 720
+
+// Number of procedurally generated points standing in for the DESI catalog.
+// This is replaced by real survey data once ingestion lands.
+POINT_COUNT :: 4_000
+WORLD_RADIUS :: f32(500.0)
+
+Galaxy :: struct {
+	position: rl.Vector3,
+	color:    rl.Color,
+}
+
+camera: rl.Camera3D
+universe: [dynamic]Galaxy
+
+// Deterministic generator so the placeholder sky is stable between runs.
+rng: rand.Default_Random_State
+
+main :: proc() {
+	rng = rand.create(0xDE51_0000)
+	context.random_generator = rand.default_random_generator(&rng)
+
+	rl.SetConfigFlags({.WINDOW_RESIZABLE, .VSYNC_HINT, .MSAA_4X_HINT})
+	rl.InitWindow(WIDTH, HEIGHT, "DESI Explorer")
+	defer rl.CloseWindow()
+	rl.SetTargetFPS(60)
+
+	camera = make_camera()
+	make_universe(&universe, POINT_COUNT)
+	defer delete(universe)
+
+	for !rl.WindowShouldClose() {
+		update()
+		draw()
+	}
+}
+
+make_camera :: proc() -> rl.Camera3D {
+	return {
+		position = {0, 220, 220},
+		target = {0, 0, 0},
+		up = {0, 1, 0},
+		fovy = 60,
+		projection = .PERSPECTIVE,
+	}
+}
+
+make_universe :: proc(u: ^[dynamic]Galaxy, count: int) {
+	clear(u)
+	reserve(u, count)
+	for _ in 0 ..< count {
+		pos := random_sphere_point(WORLD_RADIUS)
+		append(u, Galaxy{position = pos, color = color_for_position(pos)})
+	}
+}
+
+// Uniformly distributed random point inside the scene's bounding sphere.
+random_sphere_point :: proc(radius: f32) -> rl.Vector3 {
+	for {
+		x := rand.float32_range(-1, 1)
+		y := rand.float32_range(-1, 1)
+		z := rand.float32_range(-1, 1)
+		len_sq := x * x + y * y + z * z
+		if len_sq > 0.0001 && len_sq < 1.0 {
+			return {x * radius, y * radius, z * radius}
+		}
+	}
+}
+
+// Maps distance from the origin to a blue (near) -> red (far) gradient, a
+// stand-in for redshift until real colors are computed from survey metadata.
+color_for_position :: proc(p: rl.Vector3) -> rl.Color {
+	d := math.sqrt(p.x * p.x + p.y * p.y + p.z * p.z)
+	t := math.clamp(d / WORLD_RADIUS, 0, 1)
+	return rl.Color{u8(40 + 180 * t), 120, u8(255 - 180 * t), 255}
+}
+
+update :: proc() {
+	// Orbital camera: drag to rotate, scroll to zoom, right-drag / shift to pan.
+	rl.UpdateCamera(&camera, .ORBITAL)
+}
+
+draw :: proc() {
+	rl.BeginDrawing()
+	defer rl.EndDrawing()
+
+	rl.ClearBackground({5, 5, 15, 255})
+
+	rl.BeginMode3D(camera)
+	defer rl.EndMode3D()
+
+	rl.DrawGrid(20, 50.0)
+
+	for galaxy in universe {
+		rl.DrawPoint3D(galaxy.position, galaxy.color)
+	}
+
+	rl.DrawFPS(10, 10)
+	rl.DrawText(
+		"DESI Explorer — drag to rotate, scroll to zoom",
+		10,
+		34,
+		18,
+		rl.RAYWHITE,
+	)
+}