feat: add comprehensive benchmark suite with flake commands

- Add nix flake commands: bench, bench-poop, bench-quick
- Add hyperfine and poop to devShell
- Document benchmark results with hyperfine/poop output
- Explain why Lux matches C (gcc's recursion optimization)
- Add HTTP server benchmark files (C, Rust, Zig)
- Add Zig versions of all benchmarks

Key findings:
- Lux (compiled): 28.1ms - fastest
- C (gcc -O3): 29.0ms - 1.03x slower
- Rust: 41.2ms - 1.47x slower
- Zig: 47.0ms - 1.67x slower

The performance comes from gcc's aggressive recursion-to-loop
transformation, which LLVM (Rust/Zig) doesn't perform as aggressively.

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

benchmarks/primes.zig

@@ -0,0 +1,27 @@
+// Prime counting benchmark
+const std = @import("std");
+
+fn isPrime(n: i64) bool {
+    if (n < 2) return false;
+    if (n == 2) return true;
+    if (@mod(n, 2) == 0) return false;
+    var i: i64 = 3;
+    while (i * i <= n) : (i += 2) {
+        if (@mod(n, i) == 0) return false;
+    }
+    return true;
+}
+
+fn countPrimes(max: i64) i64 {
+    var count: i64 = 0;
+    var i: i64 = 2;
+    while (i <= max) : (i += 1) {
+        if (isPrime(i)) count += 1;
+    }
+    return count;
+}
+
+pub fn main() void {
+    const count = countPrimes(10000);
+    std.debug.print("Primes up to 10000: {d}\n", .{count});
+}