fix: Update .gitignore and remove dev files from repository

Remove development and investigation files that shouldn't be in repo:
- Kate editor swap files (*.swp, *.kate-swp)
- Discord development folder (contains credentials)
- Development investigation scripts (db_investigation.sh, etc.)
- Configuration files (docker-compose.dev.yml)

Note: Files removed from git but kept locally (rm --cached)
Files are still present in working directory but won't be tracked

.gitignore

@@ -445,4 +445,26 @@ TEST-CLONE.md
 !docs/API.md
 !docs/CONFIGURATION.md
 !docs/ARCHITECTURE.md
-!docs/DEVELOPMENT.md
+!docs/DEVELOPMENT.md
+
+# =============================================================================
+# Development and investigation files (should not be in repo)
+# =============================================================================
+db_investigation.sh
+fix_agent_permissions.sh
+install.sh
+docker-compose.dev.yml
+.migration_temp/
+
+# =============================================================================
+# Kate editor swap files
+# =============================================================================
+*.swp
+*.kate-swp
+.MIGRATION_STRATEGY.md.kate-swp
+
+# =============================================================================
+# Discord bot development (private, contains credentials)
+# =============================================================================
+discord/
+discord/.env.example