Enable strictNullChecks, eqeqeq (#436)

## Description:

Improve type safety and runtime correctness by:
1. Enabling TypeScript's
[strictNullChecks](https://www.typescriptlang.org/tsconfig/#strictNullChecks)
compiler option.
2. Replacing all loose equality operators (`==` and `!=`) with strict
equality operators (`===` and `!==`).
3. Cleaning up of type declarations, null handling logic, and equality
expressions throughout the project.

Currently, the code allows implicit assumptions that `null` and
`undefined` are interchangeable, and relies on type-coercing equality
checks that can introduce subtle bugs. These practices make it difficult
to reason about when values may be absent and hinder the effectiveness
of static analysis.

Migrating to strict null checks and enforcing strict equality
comparisons will clarify intent, reduce bugs, and make the codebase
safer and easier to maintain.

Fixes #466 

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

---------

Co-authored-by: Scott Anderson <662325+scottanderson@users.noreply.github.com>
Co-authored-by: evanpelle <openfrontio@gmail.com>

src/client/HostLobbyModal.ts

@@ -31,7 +31,6 @@ export class HostLobbyModal extends LitElement {
   @state() private disableNPCs = false;
   @state() private gameMode: GameMode = GameMode.FFA;
   @state() private teamCount: number | typeof Duos = 2;
-  @state() private disableNukes: boolean = false;
   @state() private bots: number = 400;
   @state() private infiniteGold: boolean = false;
   @state() private infiniteTroops: boolean = false;
@@ -40,9 +39,9 @@ export class HostLobbyModal extends LitElement {
   @state() private copySuccess = false;
   @state() private players: string[] = [];
   @state() private useRandomMap: boolean = false;
-  @state() private disabledUnits: string[] = [];
+  @state() private disabledUnits: UnitType[] = [];
 
-  private playersInterval = null;
+  private playersInterval: NodeJS.Timeout | null = null;
   // Add a new timer for debouncing bot changes
   private botsUpdateTimer: number | null = null;
 
@@ -106,7 +105,7 @@ export class HostLobbyModal extends LitElement {
                               .selected=${!this.useRandomMap &&
                               this.selectedMap === mapValue}
                               .translation=${translateText(
-                                `map.${mapKey.toLowerCase()}`,
+                                `map.${mapKey?.toLowerCase()}`,
                               )}
                             ></map-display>
                           </div>
@@ -233,7 +232,7 @@ export class HostLobbyModal extends LitElement {
                 />
                 <div class="option-card-title">
                   <span>${translateText("host_modal.bots")}</span>${
-                    this.bots == 0
+                    this.bots === 0
                       ? translateText("host_modal.bots_disabled")
                       : this.bots
                   }
@@ -326,7 +325,7 @@ export class HostLobbyModal extends LitElement {
                     [UnitType.HydrogenBomb, "unit_type.hydrogen_bomb"],
                     [UnitType.MIRV, "unit_type.mirv"],
                   ].map(
-                    ([unitType, translationKey]) => html`
+                    ([unitType, translationKey]: [UnitType, string]) => html`
                       <label
                         class="option-card ${this.disabledUnits.includes(
                           unitType,
@@ -405,7 +404,7 @@ export class HostLobbyModal extends LitElement {
             }
           </button>
         </div>
-					
+
       </div>
     </o-modal>
     `;
@@ -503,10 +502,6 @@ export class HostLobbyModal extends LitElement {
     this.infiniteTroops = Boolean((e.target as HTMLInputElement).checked);
     this.putGameConfig();
   }
-  private handleDisableNukesChange(e: Event) {
-    this.disableNukes = Boolean((e.target as HTMLInputElement).checked);
-    this.putGameConfig();
-  }
 
   private async handleDisableNPCsChange(e: Event) {
     this.disableNPCs = Boolean((e.target as HTMLInputElement).checked);
@@ -537,16 +532,14 @@ export class HostLobbyModal extends LitElement {
           gameMap: this.selectedMap,
           difficulty: this.selectedDifficulty,
           disableNPCs: this.disableNPCs,
-          disableNukes: this.disableNukes,
           bots: this.bots,
           infiniteGold: this.infiniteGold,
           infiniteTroops: this.infiniteTroops,
           instantBuild: this.instantBuild,
           gameMode: this.gameMode,
-          numPlayerTeams: this.teamCount,
           disabledUnits: this.disabledUnits,
           playerTeams: this.teamCount,
-        } as GameConfig),
+        } satisfies Partial<GameConfig>),
       },
     );
     return response;
@@ -607,7 +600,7 @@ export class HostLobbyModal extends LitElement {
       .then((response) => response.json())
       .then((data: GameInfo) => {
         console.log(`got game info response: ${JSON.stringify(data)}`);
-        this.players = data.clients.map((p) => p.username);
+        this.players = data.clients?.map((p) => p.username) ?? [];
       });
   }
 }