Add IP information API with background WHOIS fetcher

- Add /ip and /ip/{addr} JSON endpoints returning comprehensive IP info
- Include ASN, netblock, country code, org name, abuse contact, RIR data
- Extend ASN schema with WHOIS fields (country, org, abuse contact, etc)
- Create background WHOIS fetcher for rate-limited ASN info updates
- Store raw WHOIS responses for debugging and data preservation
- Queue on-demand WHOIS lookups when stale data is requested
- Refactor handleIPInfo to serve all IP endpoints consistently

internal/database/schema.sql

@@ -6,8 +6,25 @@ CREATE TABLE IF NOT EXISTS asns (
 	asn INTEGER PRIMARY KEY,
 	handle TEXT,
 	description TEXT,
+	-- WHOIS parsed fields
+	as_name TEXT,
+	org_name TEXT,
+	org_id TEXT,
+	address TEXT,                -- full address (may be multi-line)
+	country_code TEXT,
+	abuse_email TEXT,
+	abuse_phone TEXT,
+	tech_email TEXT,
+	tech_phone TEXT,
+	rir TEXT,                    -- ARIN, RIPE, APNIC, LACNIC, AFRINIC
+	rir_registration_date DATETIME,
+	rir_last_modified DATETIME,
+	-- Raw WHOIS response
+	whois_raw TEXT,              -- complete WHOIS response text
+	-- Timestamps
 	first_seen DATETIME NOT NULL,
-	last_seen DATETIME NOT NULL
+	last_seen DATETIME NOT NULL,
+	whois_updated_at DATETIME    -- when we last fetched WHOIS data
 );
 
 -- IPv4 prefixes table