improve main.zig based on established zig project patterns

- add thread_safe = true to GPA (required for multi-threaded usage)
- use detach() instead of misleading defer join() (consumer never returns)
- switch from debug.print to std.log.scoped for proper log levels
- group imports: stdlib → external → internal

patterns verified against ghostty, tigerbeetle, zap, http.zig

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

src/main.zig

···
 const net = std.net;
 const posix = std.posix;
 const Thread = std.Thread;
+
 const http = @import("server/http.zig");
 const db = @import("stream/db.zig");
 const jetstream = @import("stream/jetstream.zig");
 const stats = @import("server/stats.zig");
+
+const log = std.log.scoped(.main);
 
 const MAX_HTTP_WORKERS = 16;
 const SOCKET_TIMEOUT_SECS = 30;
 
 pub fn main() !void {
-    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    var gpa = std.heap.GeneralPurposeAllocator(.{
+        .thread_safe = true,
+    }){};
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
 
···
     // init database
     try db.init();
 
-    // start jetstream consumer in background
+    // start jetstream consumer in background (runs forever, reconnects on error)
     const js_thread = try Thread.spawn(.{}, jetstream.consumer, .{allocator});
-    defer js_thread.join();
+    js_thread.detach();
 
     // init thread pool for http connections
     var pool: Thread.Pool = undefined;
···
     var server = try address.listen(.{ .reuse_address = true });
     defer server.deinit();
 
-    std.debug.print("zig-bsky-feed listening on http://0.0.0.0:{d}\n", .{port});
+    log.info("listening on http://0.0.0.0:{d}", .{port});
 
     while (true) {
         const conn = server.accept() catch |err| {
-            std.debug.print("accept error: {}\n", .{err});
+            log.err("accept error: {}", .{err});
             continue;
         };
 
         setSocketTimeout(conn.stream.handle, SOCKET_TIMEOUT_SECS) catch |err| {
-            std.debug.print("failed to set socket timeout: {}\n", .{err});
+            log.warn("failed to set socket timeout: {}", .{err});
         };
 
         pool.spawn(http.handleConnection, .{conn}) catch |err| {
-            std.debug.print("pool spawn error: {}\n", .{err});
+            log.err("pool spawn error: {}", .{err});
             conn.stream.close();
         };
     }