fix: add input validation to analytics app schemas

[pedroccastro]

What does this PR do?

Adds input validation to analytics app integration schemas. Tracking IDs and URLs now conform to their expected formats, preventing malformed data from being stored and rendered.

Changes

Layer	File(s)	Change
Schema	gtm/zod.ts	Validate GTM-XXXXXX format
Schema	ga4/zod.ts	Validate G-XXXXXXXXXX format
Schema	metapixel/zod.ts	Validate numeric pixel IDs
Schema	posthog/zod.ts	Validate alphanumeric keys + http/https URLs
Schema	fathom/zod.ts	Validate alphanumeric site IDs
Schema	plausible/zod.ts	Validate domain format + http/https URLs
Schema	matomo/zod.ts	Validate http/https URLs + numeric site IDs
Schema	umami/zod.ts	Validate UUID/numeric IDs + http/https URLs
Schema	twipla/zod.ts	Validate alphanumeric/UUID site IDs
Schema	insihts/zod.ts	Validate alphanumeric site IDs + http/https URLs
Schema	databuddy/zod.ts	Validate alphanumeric client IDs + http/https URLs
Tests	analytics-apps.test.ts	Unit tests for all schemas

Technical Details

• URL fields use new URL() for validation + protocol check (http/https only)
• Tracking IDs use format-specific regex based on each provider's documentation
• Empty strings remain valid for optional fields (backwards compatible)

How should this be tested?

1. Configure any analytics app on an event type with valid ID → should save
2. Try saving with invalid format (e.g., letters in Meta Pixel ID) → should show validation error
3. Leave optional fields empty → should save successfully
4. Run unit tests: yarn vitest run packages/app-store/analytics-apps.test.ts

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code.
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

[github-actions]

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