feat(extraction): enhance thumbnail URL validation with strict HTTP 200 check

- Implement strict HTTP 200 validation (reject all other status codes)
- Add content-type validation (must be image/*)
- Add 10-second timeout protection with AbortController
- Thread progressCallback through all fetchImageAsBase64 calls
- Add detailed logging for each validation failure scenario
- Report validation failures via SSE progress callbacks

Unit tests:
- Add comprehensive test coverage for all validation scenarios
- Test HTTP status codes (200, 404, 403, 500, etc.)
- Test content-type validation (image/* vs text/html, etc.)
- Test timeout behavior with AbortController
- Test error handling (network errors, DNS, SSL, etc.)
- Test progress callback reporting

Integration tests:
- Add tests for complete extraction flow with URL failures
- Test fallback chain behavior (meta tags → poster → Instagram data → screenshot)
- Test real-world scenarios (redirects, query params, different post types)

Documentation:
- Enhanced JSDoc with validation criteria
- Added examples showing fallback behavior
- Documented all failure scenarios and their handling

All tests passing ✅

secrets/auth.json

@@ -5,7 +5,7 @@
       "value": "SDRORLyWEsWWty2ZoVGdER",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1800850825.03515,
+      "expires": 1800851069.9794,
       "httpOnly": false,
       "secure": true,
       "sameSite": "Lax"
@@ -45,7 +45,7 @@
       "value": "59661903731",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1774066825.035238,
+      "expires": 1774067069.979487,
       "httpOnly": false,
       "secure": true,
       "sameSite": "None"
@@ -55,7 +55,7 @@
       "value": "1280x720",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1766895625,
+      "expires": 1766895870,
       "httpOnly": false,
       "secure": true,
       "sameSite": "Lax"
@@ -72,7 +72,7 @@
     },
     {
       "name": "rur",
-      "value": "\"CLN\\05459661903731\\0541797826824:01fe2bf80cb1bddd6aea685051ab1e074bc8a96e8f130d164433c7ccb25131cc99964a3b\"",
+      "value": "\"CLN\\05459661903731\\0541797827069:01fe263659ed914f1ffebb931cb01384ada1b8d59314115427d88c227c8b8dd50b867ce3\"",
       "domain": ".instagram.com",
       "path": "/",
       "expires": -1,
@@ -87,7 +87,7 @@
       "localStorage": [
         {
           "name": "chatd-deviceid",
-          "value": "81c8375c-7599-4dd6-b3c4-bc52a4152832"
+          "value": "77312b9f-46de-4a13-bc4c-c0b033527fed"
         },
         {
           "name": "hb_timestamp",
@@ -95,7 +95,7 @@
         },
         {
           "name": "IGSession",
-          "value": "6m2tlb:1766292624224"
+          "value": "6m2tlb:1766292870184"
         },
         {
           "name": "pixel_fire_ts",
@@ -107,7 +107,7 @@
         },
         {
           "name": "Session",
-          "value": "04nhug:1766290859223"
+          "value": "jkk7vp:1766291105184"
         },
         {
           "name": "has_interop_upgraded",