[Task](Template App): Migrate to new Vite-React-TypeScript ESLint configuration

[ArtieReus]

Task Description

Migrate the template app from the current mixed JavaScript/TypeScript ESLint configuration (juno-typescript.mjs) to the new pure TypeScript configuration (vite-react-ts.mjs). This will eliminate the need for
rule override workarounds and enable strict TypeScript checking aligned with Vite's default setup.

Sub-tasks

• Update eslint.config.mjs to import and use the new vite-react-ts.mjs configuration from @cloudoperators/juno-config
• Remove all existing TypeScript rule override workarounds (currently 15-20 rules being disabled)
• Fix any new TypeScript errors/warnings surfaced by strict type checking
• Ensure remaining rule overrides are ≤5 and each has a justification comment explaining why it's necessary
• Test that ESLint runs successfully in development and CI
• Verify the app builds and runs correctly after migration
• Remove references to old juno-typescript.mjs configuration
• Update any related documentation

Related Issues

Epic: #1565 - ESLint Configuration Migration to Vite-React-TypeScript Standards

Additional Context

Current State:

• Template app uses mixed JS/TS configuration from juno-typescript.mjs
• Requires 15-20 TypeScript rule overrides as workarounds
• Mixing pluginJs.configs.recommended with tseslint.configs.recommendedTypeCheckedOnly causes conflicts

Target State:

• Use new pure TypeScript configuration vite-react-ts.mjs
• Minimal overrides (≤5 rules) with justification comments
• Strict TypeScript checking enabled
• Aligned with Vite's default ESLint setup
• Better type safety and developer experience

Migration Pattern:
This follows the epic's three-phase approach. Template app is one of 7 apps being migrated in parallel during Phase 2. The old config will be retained until all apps/packages complete migration (Phase 3).