fix: normalize root_path_skip_prefixes in ProcessLinksMiddleware

[lhoupert]

Addressing edge case 1 in #200: If you pass a skip prefix with a trailing slash straight to the middleware (e.g. ["/raster/"]), it never matches any link. The skip list just stops working and links to sibling apps get ROOT_PATH added again (the issue #198 tried to prevent). Configuration via env vars is unaffected as the Settings validator normalizes the prefixes (strips trailing slashes, drops empties) before they reach the middleware, but not ProcessLinksMiddleware when it is constructed directly (prefixes passed directly to ProcessLinksMiddleware dont get such normalization)

[claude]

Claude finished @lhoupert's task in 1m 2s —— View job

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Review complete

• Gather context (diff, related code)
• Review correctness/security/best-practices
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✅ No blocking issues — safe to merge.

The fix is minimal and correctly targeted: ProcessLinksMiddleware.__post_init__ (src/stac_auth_proxy/middleware/ProcessLinksMiddleware.py:34-40) normalizes root_path_skip_prefixes the same way config.py's parse_root_path_skip_prefixes validator does (strip trailing /, drop empties), fixing the gap where prefixes passed directly to the middleware (bypassing Settings) weren't normalized.

• Confirmed JsonResponseMiddleware (the parent class) has no existing __post_init__ to shadow, so this doesn't skip any inherited initialization.
• tuple(...) construction doesn't mutate the caller's original list, and dataclass field reassignment is safe here.
• The new test case (tests/test_process_links.py:560-571) directly reproduces the reported bug (["/raster/"] silently matching nothing) and verifies the fix.
• Edge case of a single "/" prefix rstrips to "" and is silently dropped — consistent with the config-layer behavior in spirit (config raises there, middleware just drops), which is a reasonable difference since this layer only normalizes rather than validates.

No security or correctness concerns. No test or lint gaps.

Simplify (ponytail)

Nothing to cut — this is already the minimal fix (one __post_init__, no new abstractions).

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💰 Estimated review cost: $0.41 · 1m01s · 15 turns