Add coordinate validation and ESLint integration

- Add explicit latitude/longitude validation in location submissions
- Implement ESLint with TypeScript support and flat config
- Auto-fix 621 formatting issues across codebase
- Add comprehensive tests for coordinate validation
- Update documentation with lint scripts and validation rules
- Maintain 128 passing tests with enhanced security

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/setup.ts

@@ -16,7 +16,7 @@ export const createTestDatabase = (): Promise<Database> => {
         reject(err);
         return;
       }
-      
+
       // Create locations table
       db.run(`
         CREATE TABLE IF NOT EXISTS locations (
@@ -48,7 +48,7 @@ export const createTestProfanityDatabase = (): Promise<Database> => {
         reject(err);
         return;
       }
-      
+
       // Create profanity_words table
       db.run(`
         CREATE TABLE IF NOT EXISTS profanity_words (