refactor: move streamable HTTP app creation from FastMCP to lowlevel … #213

Job	Run time
checks / pre-commit	39s
checks / readme-snippets	14s
checks / test (3.11, lowest-direct, windows-latest)	2m 25s
checks / test (3.10, locked, ubuntu-latest)	46s
checks / test (3.12, locked, ubuntu-latest)	49s
checks / test (3.10, lowest-direct, windows-latest)	2m 21s
checks / test (3.10, locked, windows-latest)	2m 31s
checks / test (3.11, lowest-direct, ubuntu-latest)	49s
checks / test (3.12, locked, windows-latest)	3m 21s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, locked, ubuntu-latest)	46s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.12, lowest-direct, windows-latest)	3m 26s
checks / test (3.14, lowest-direct, windows-latest)	2m 18s
checks / test (3.13, locked, windows-latest)	2m 22s
checks / test (3.11, locked, windows-latest)	2m 34s
checks / test (3.14, locked, windows-latest)	3m 4s
checks / test (3.13, lowest-direct, windows-latest)	2m 26s
checks / test (3.13, locked, ubuntu-latest)	43s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.14, locked, ubuntu-latest)	2m 21s
all-green	5s
	37m 28s

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