Add eBay Browse API integration with daily call quota

eBay marketplaces are now polled through eBay's official Buy > Browse API (client-credentials OAuth2) instead of an Apify scraper actor; Apify still handles Yahoo JP and Mercari. Browse API calls are tracked per day in a new ebay_api_usage table and capped (default 5000, configurable) on eBay's Pacific-time reset clock, so polling halts before the limit is hit. Credentials live in config.toml [ebay] and are overridable via /settings, which also surfaces the day's running call count.

Also carries the server.secure_cookies config plumbing (field, accessor, example) consumed by the following commit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/db/schema.sql

@@ -90,6 +90,15 @@ INSERT OR IGNORE INTO settings (key, value) VALUES
     ('global_poll_interval_minutes', '60'),
     ('match_confidence_threshold', '0.6');
 
+-- ebay_api_usage tracks Browse API calls per day so Veola can surface
+-- consumption and halt polling before the developer keyset's daily call
+-- limit is exceeded. usage_date is YYYY-MM-DD in US Pacific time, matching
+-- eBay's own quota reset.
+CREATE TABLE IF NOT EXISTS ebay_api_usage (
+    usage_date TEXT PRIMARY KEY,
+    call_count INTEGER NOT NULL DEFAULT 0
+);
+
 CREATE TABLE IF NOT EXISTS sessions (
     token  TEXT PRIMARY KEY,
     data   BLOB NOT NULL,