fix: resolve all TypeScript type errors across codebase for Deno strict mode

Comprehensive type safety improvements across all CLI handlers and daemon:

**Error handling type fixes:**
- Add 'error instanceof Error' checks before accessing error.message throughout
- Fix all error/retryError/stdError/upsError type assertions
- Replace direct error.message with proper type guards

**Switch case improvements:**
- Wrap case block declarations in braces to satisfy deno-lint
- Fix no-case-declarations warnings in CLI command handlers

**Null/undefined safety:**
- Add checks for config.snmp and config.thresholds before access
- Fix IUpsStatus lastStatusChange to handle undefined with default value
- Add proper null checks in legacy configuration paths

**Type annotations:**
- Add explicit type annotations to lambda parameters (groupId, updateAvailable, etc.)
- Add TUpsModel type cast for 'cyberpower' default
- Import and use INupstConfig type where needed

**Parameter type fixes:**
- Fix implicit 'any' type errors in array callbacks
- Add type annotations to filter/find/map parameters

Files modified:
- ts/cli.ts: config.snmp/thresholds null checks, unused error variable fixes
- ts/cli/group-handler.ts: 4 error.message fixes + 2 parameter type annotations
- ts/cli/service-handler.ts: 3 error.message fixes
- ts/cli/ups-handler.ts: 5 error.message fixes + config checks + TUpsModel import
- ts/daemon.ts: 8 error.message fixes + IUpsStatus lastStatusChange fix + updateAvailable type
- ts/nupst.ts: 1 error.message fix
- ts/systemd.ts: 5 error.message fixes + parameter type annotation

All tests passing (3/3 SNMP tests + 10/10 logger tests)
Type check: ✓ No errors

ts/systemd.ts

@@ -81,7 +81,7 @@ WantedBy=multi-user.target
       logger.logBoxLine('Service enabled to start on boot');
       logger.logBoxEnd();
     } catch (error) {
-      if (error.message === 'Configuration not found') {
+      if (error instanceof Error && error.message === 'Configuration not found') {
         // Just rethrow the error as the message has already been displayed
         throw error;
       }
@@ -105,7 +105,7 @@ WantedBy=multi-user.target
       logger.logBoxLine('NUPST service started successfully');
       logger.logBoxEnd();
     } catch (error) {
-      if (error.message === 'Configuration not found') {
+      if (error instanceof Error && error.message === 'Configuration not found') {
         // Exit with error code since configuration is required
         process.exit(1);
       }
@@ -157,7 +157,7 @@ WantedBy=multi-user.target
       await this.displayServiceStatus();
       await this.displayAllUpsStatus();
     } catch (error) {
-      logger.error(`Failed to get status: ${error.message}`);
+      logger.error(`Failed to get status: ${error instanceof Error ? error.message : String(error)}`);
     }
   }
 
@@ -219,7 +219,7 @@ WantedBy=multi-user.target
     } catch (error) {
       const boxWidth = 45;
       logger.logBoxTitle('UPS Status', boxWidth);
-      logger.logBoxLine(`Failed to retrieve UPS status: ${error.message}`);
+      logger.logBoxLine(`Failed to retrieve UPS status: ${error instanceof Error ? error.message : String(error)}`);
       logger.logBoxEnd();
     }
   }
@@ -239,8 +239,8 @@ WantedBy=multi-user.target
     if (ups.groups && ups.groups.length > 0) {
       // Get group names if available
       const config = this.daemon.getConfig();
-      const groupNames = ups.groups.map(groupId => {
-        const group = config.groups?.find(g => g.id === groupId);
+      const groupNames = ups.groups.map((groupId: string) => {
+        const group = config.groups?.find((g: { id: string }) => g.id === groupId);
         return group ? group.name : groupId;
       });
       logger.logBoxLine(`Groups: ${groupNames.join(', ')}`);
@@ -275,7 +275,7 @@ WantedBy=multi-user.target
       logger.logBoxEnd();
     } catch (error) {
       logger.logBoxTitle(`UPS Status: ${ups.name}`, boxWidth);
-      logger.logBoxLine(`Failed to retrieve UPS status: ${error.message}`);
+      logger.logBoxLine(`Failed to retrieve UPS status: ${error instanceof Error ? error.message : String(error)}`);
       logger.logBoxEnd();
     }
   }