test: fix 4 remaining doc test failures from CI

- distributed-locking.md: Add notest to db.generate_report example
- adaptive-timeouts.md: Add notest to db.query example
- serializer-guide.md: Add notest to fetch_user_from_db example
- getting-started.md: Relax timing assertion from 10ms to 100ms for CI

All 131 doc tests now pass locally.

Author: 27Bslash6

docs/features/adaptive-timeouts.md

@@ -177,7 +177,8 @@ def operation(x):
 ## How to Use It
 
 ### Basic Usage (Automatic)
-```python
+```python notest
+# Illustrative example - requires database connection
 @cache(ttl=3600)  # Adaptive timeout enabled
 def get_user(user_id):
     return db.query(user_id)

docs/features/distributed-locking.md

@@ -26,7 +26,8 @@ def expensive_query(key):
 
 Distributed locking enabled by default:
 
-```python
+```python notest
+# Illustrative example - requires database connection
 from cachekit import cache
 
 @cache(ttl=300)  # Locking active

docs/getting-started.md

@@ -363,7 +363,7 @@ duration2 = time.time() - start
 print(f"Second call: {duration2:.3f}s, Result: {result2}")
 
 assert result1 == result2
-assert duration2 < 0.01  # Cache hit should be <10ms
+assert duration2 < 0.1  # Cache hit should be <100ms (generous for CI)
 print("Caching working correctly!")
 ```
 

docs/guides/serializer-guide.md

@@ -405,7 +405,8 @@ def get_user(user_id: int) -> User:
 
 **Best practice** - Convert to dict before caching (explicit and efficient):
 
-```python
+```python notest
+# Illustrative example showing Pydantic model handling pattern
 from pydantic import BaseModel
 from cachekit import cache