Initial lookbook implementation

Pinterest-style visual bookmarking app with:
- URL metadata extraction (OG/Twitter meta, oEmbed fallback)
- Image caching in Postgres with 480px thumbnails
- Multi-tag filtering with Ctrl/Cmd for OR mode
- Fuzzy tag suggestions and inline tag editing
- Browser console auth() with first-use password setup
- Brutalist UI with Commit Mono font and Pico CSS
- Light/dark mode via browser preference

vendor/github.com/jackc/puddle/v2/log.go

@@ -0,0 +1,32 @@
+package puddle
+
+import "unsafe"
+
+type ints interface {
+	int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
+}
+
+// log2Int returns log2 of an integer. This function panics if val < 0. For val
+// == 0, returns 0.
+func log2Int[T ints](val T) uint8 {
+	if val <= 0 {
+		panic("log2 of non-positive number does not exist")
+	}
+
+	return log2IntRange(val, 0, uint8(8*unsafe.Sizeof(val)))
+}
+
+func log2IntRange[T ints](val T, begin, end uint8) uint8 {
+	length := end - begin
+	if length == 1 {
+		return begin
+	}
+
+	delim := begin + length/2
+	mask := T(1) << delim
+	if mask > val {
+		return log2IntRange(val, begin, delim)
+	} else {
+		return log2IntRange(val, delim, end)
+	}
+}