refactor: replace source file copies with README links

- Replace redundant Factorial.hs copy with README link to plinth/src/Factorial.hs
- Add README.md files to existing Plinth fibonacci submissions
- Use relative paths (../../../../plinth/src/) for GitHub navigation
- Eliminates duplicate source code maintenance
- Provides clear navigation to original implementation

Author: Unisay

submissions/factorial/Plinth_1.52.0.0_Unisay/source/Factorial.hs

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+# Source Code
+
+The source code for this factorial implementation is located in the main repository:
+
+**[📁 plinth/src/Factorial.hs](../../../../plinth/src/Factorial.hs)**
+
+This Haskell module contains:
+
+- `factorial :: Integer -> Integer` - The factorial function implementation
+- `factorial10Code :: CompiledCode Integer` - The compiled UPLC program for factorial(10)
+
+The implementation uses recursive approach: `factorial(n) = if n <= 0 then 1 else n * factorial(n-1)`

submissions/factorial/Plinth_1.52.0.0_Unisay/source/README.md

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+# Source Code
+
+The source code for this fibonacci implementation is located in the main repository:
+
+**[📁 plinth/src/Fibonacci.hs](../../../../plinth/src/Fibonacci.hs)**
+
+This Haskell module contains:
+
+- `fibonacci :: Integer -> Integer` - The fibonacci function implementation
+- `fibonacci25Code :: CompiledCode Integer` - The compiled UPLC program for fibonacci(25)
+
+The implementation uses recursive approach: `fibonacci(n) = if n <= 1 then n else fibonacci(n-1) + fibonacci(n-2)`
+
+**Note**: This submission was created with Plinth 1.49.0.0, while the current source uses 1.52.0.0. The core algorithm remains the same.

submissions/fibonacci/Plinth_1.49.0.0_Unisay/source/README.md

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+# Source Code
+
+The source code for this fibonacci implementation is located in the main repository:
+
+**[📁 plinth/src/Fibonacci.hs](../../../../plinth/src/Fibonacci.hs)**
+
+This Haskell module contains:
+
+- `fibonacci :: Integer -> Integer` - The fibonacci function implementation
+- `fibonacci25Code :: CompiledCode Integer` - The compiled UPLC program for fibonacci(25)
+
+The implementation uses recursive approach: `fibonacci(n) = if n <= 1 then n else fibonacci(n-1) + fibonacci(n-2)`