fix: implement comprehensive UI/UX and code organization improvements

CSRF Form Enhancements:
- Add optional onError callback prop for better error handling
- Remove CSRF token from console logging for security
- Provide user-friendly error notifications instead of silent failures

Date Filter Optimization:
- Refactor sessions route to avoid object mutation issues
- Build date filters cleanly without relying on spreading existing objects
- Prevent potential undefined startTime mutations

Geographic Threat Map Optimization:
- Extract country names to reusable constants in lib/constants/countries.ts
- Calculate max values once to avoid repeated expensive operations
- Centralize threat level color mapping to eliminate duplicated logic
- Replace repeated color assignments with centralized THREAT_LEVELS configuration

Accessibility Improvements:
- Add keyboard support to audit log table rows (Enter/Space keys)
- Include proper ARIA labels and focus management
- Add tabIndex for screen reader compatibility
- Enhance focus indicators with ring styling

Performance & Code Organization:
- Move COUNTRY_NAMES to shared constants for reusability
- Optimize calculation patterns in threat mapping components
- Reduce redundant logic and improve maintainability

lib/constants/countries.ts

@@ -0,0 +1,84 @@
+/**
+ * Country Constants
+ *
+ * Country code to name mapping for common countries
+ * Used throughout the application for geographic data display
+ */
+
+export const COUNTRY_NAMES: Record<string, string> = {
+  USA: "United States",
+  GBR: "United Kingdom",
+  DEU: "Germany",
+  FRA: "France",
+  JPN: "Japan",
+  CHN: "China",
+  IND: "India",
+  BRA: "Brazil",
+  CAN: "Canada",
+  AUS: "Australia",
+  RUS: "Russia",
+  ESP: "Spain",
+  ITA: "Italy",
+  NLD: "Netherlands",
+  KOR: "South Korea",
+  MEX: "Mexico",
+  CHE: "Switzerland",
+  SWE: "Sweden",
+  NOR: "Norway",
+  DNK: "Denmark",
+  FIN: "Finland",
+  POL: "Poland",
+  BEL: "Belgium",
+  AUT: "Austria",
+  NZL: "New Zealand",
+  SGP: "Singapore",
+  THA: "Thailand",
+  IDN: "Indonesia",
+  MYS: "Malaysia",
+  PHL: "Philippines",
+  VNM: "Vietnam",
+  ARE: "UAE",
+  SAU: "Saudi Arabia",
+  ISR: "Israel",
+  ZAF: "South Africa",
+  EGY: "Egypt",
+  TUR: "Turkey",
+  GRC: "Greece",
+  PRT: "Portugal",
+  CZE: "Czech Republic",
+  HUN: "Hungary",
+  ROU: "Romania",
+  BGR: "Bulgaria",
+  HRV: "Croatia",
+  SVN: "Slovenia",
+  SVK: "Slovakia",
+  EST: "Estonia",
+  LVA: "Latvia",
+  LTU: "Lithuania",
+  LUX: "Luxembourg",
+  MLT: "Malta",
+  CYP: "Cyprus",
+  ISL: "Iceland",
+  IRL: "Ireland",
+  ARG: "Argentina",
+  CHL: "Chile",
+  COL: "Colombia",
+  PER: "Peru",
+  URY: "Uruguay",
+  ECU: "Ecuador",
+  BOL: "Bolivia",
+  PRY: "Paraguay",
+  VEN: "Venezuela",
+  UKR: "Ukraine",
+  BLR: "Belarus",
+  MDA: "Moldova",
+  GEO: "Georgia",
+  ARM: "Armenia",
+  AZE: "Azerbaijan",
+  KAZ: "Kazakhstan",
+  UZB: "Uzbekistan",
+  KGZ: "Kyrgyzstan",
+  TJK: "Tajikistan",
+  TKM: "Turkmenistan",
+  MNG: "Mongolia",
+};