Fix database connection pool leak in init_db()

- Check if pool already exists before creating a new one
- Set pool size limits (min=2, max=10) to prevent exhaustion
- Multiple calls to init_db() were creating new pools without
  closing old ones, leading to "too many clients" errors

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test_simple.sexp

@@ -0,0 +1,26 @@
+;; Simple Test - No external assets required
+;; Just generates a color gradient that changes over time
+
+(stream "simple_test"
+  :fps 30
+  :width 720
+  :height 720
+  :seed 42
+
+  ;; Load standard primitives
+  (require-primitives "geometry")
+  (require-primitives "core")
+  (require-primitives "math")
+  (require-primitives "image")
+  (require-primitives "color_ops")
+
+  ;; Frame pipeline - animated gradient
+  (frame
+    (let [;; Time-based color cycling (0-1 range)
+          r (+ 0.5 (* 0.5 (math:sin (* t 1))))
+          g (+ 0.5 (* 0.5 (math:sin (* t 1.3))))
+          b (+ 0.5 (* 0.5 (math:sin (* t 1.7))))
+          ;; Convert to 0-255 range and create solid color frame
+          color [(* r 255) (* g 255) (* b 255)]
+          frame (image:make-image 720 720 color)]
+      frame)))