Enhance cookie jar implementation with comprehensive RFC 6265 support

This commit adds missing cookie handling cases to improve RFC 6265 compliance:

Cookie Expiration:
- Add expiration checking for both Expires and Max-Age attributes
- Max-Age takes precedence over Expires per RFC 6265
- Automatic removal of expired cookies when processing responses
- Store creation_time for accurate Max-Age calculation

Cookie Management:
- Update/replace existing cookies with same name, domain, and path
- Prevent duplicate cookie entries in the jar
- Consolidate multiple cookies into single Cookie header when sending

Domain Handling:
- Add domain validation to prevent servers from setting cookies for unrelated domains
- Case-insensitive domain matching per RFC 6265
- Handle leading dots in Domain attribute (strip per RFC 6265 Section 5.2.3)
- Subdomain matching for cookies without exact_domain flag

Path Handling:
- Implement RFC 6265 Section 5.1.4 default path computation
- Use request path minus last component when Path attribute not specified
- Fallback to "/" for edge cases

Parser Improvements:
- Add SameSite attribute support (None, Lax, Strict)
- Gracefully ignore unknown/extension cookie attributes instead of failing
- Forward compatibility with future cookie attributes

Other:
- Add time.h include for time() and time_t
- Add http_date_to_time() helper for expiration comparison
- Add is_cookie_expired() helper for expiration checks
- Add compute_default_cookie_path() per RFC 6265

chttp.h

@@ -13,6 +13,7 @@
 #include <stdbool.h>
 #include <string.h>
 #include <stdlib.h>
+#include <time.h>
 
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
@@ -257,6 +258,12 @@ typedef struct {
     int          second;
 } HTTP_Date;
 
+typedef enum {
+    HTTP_SAMESITE_NONE,
+    HTTP_SAMESITE_LAX,
+    HTTP_SAMESITE_STRICT,
+} HTTP_SameSite;
+
 typedef struct {
     HTTP_String name;
     HTTP_String value;
@@ -275,6 +282,9 @@ typedef struct {
 
     bool have_path;
     HTTP_String path;
+
+    bool have_samesite;
+    HTTP_SameSite samesite;
 } HTTP_SetCookie;
 
 // Parses a Set-Cookie header value
@@ -875,6 +885,13 @@ typedef struct {
     // This cookie can only be sent over HTTPS
     bool secure;
 
+    // Expiration information
+    bool have_expires;
+    HTTP_Date expires;
+    bool have_max_age;
+    uint32_t max_age;
+    time_t creation_time; // Unix timestamp when cookie was created
+
 } HTTP_CookieJarEntry;
 
 typedef struct {