fix: auth scheduler env vars, concurrency and browser stability

docs/outcomes/FixSchedulerConcurrencyAndBrowser.md

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+# Outcome - Fix Scheduler Concurrency and Browser Stability
+
+## Summary
+Successfully implemented fixes for the scheduler concurrency issues and browser instability.
+
+## Changes
+- **Scheduler Configuration Validation:**
+    - Updated `src/lib/server/scheduler.ts` to validate `intervalMinutes`.
+    - Added a check for `NaN` and a minimum interval of 15 minutes.
+    - Defaults to 720 minutes if the configuration is invalid.
+- **Resource Cleanup:**
+    - Refactored `renewInstagramAuth` in `src/lib/server/scheduler.ts` to use a `finally` block for closing `page` and `context`.
+    - Ensures resources are released even if an error occurs during renewal.
+- **Robust Browser Management:**
+    - Updated `src/lib/server/browser.ts` to check `browser.isConnected()`.
+    - Automatically re-initializes the browser if it is disconnected or crashed.
+
+## Verification
+- The scheduler will now default to a safe interval if misconfigured, preventing console spam.
+- Browser crashes will be automatically recovered from on the next scheduler run.
+- Resource leaks from failed renewal attempts are prevented.