feat: add media item resources

[Teagan42]

What

• expose media metadata and id lookups as FastMCP resources
• replace placeholder test fixtures with realistic movie and show data
• add positive and negative tests for new resources

Why

• allow clients to retrieve media records and their external ids via resource URIs
• ensure tests better reflect real-world scenarios and guard against failures

Affects

• mcp_plex/server.py
• tests under tests/

Testing

• uv run ruff check .
• uv run pytest
• uv run --with coverage coverage run -m pytest
• uv run --with coverage coverage report

Documentation

• n/a

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https://chatgpt.com/codex/tasks/task_e_68b3df4560ec8328be32d8a5d463e051

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex
loader.py	179	10	94%	32–34, 296, 299–302, 486, 492
server.py	85	4	95%	34–35, 208, 228
TOTAL	366	14	96%

Tests	Skipped	Failures	Errors	Time
11	0 💤	0 ❌	0 🔥	6.112s ⏱️