fix(feed): clamp invalid pagination ranges

[Jorel97]

Fixes #313.

Summary

• parse feed page and limit query params with bounded integer parsing before validation
• prevent fractional, non-finite, or extreme values from reaching Supabase .range()
• add regression coverage for fractional and non-finite pagination inputs

Tests

• Not run locally; dependencies are not installed in this workspace checkout.

[greptile-apps]

Greptile Summary

This PR replaces the bare Number(param) || default pagination pattern with a dedicated parsePaginationParam helper that validates finiteness, truncates fractions, and clamps to explicit [min, max] bounds before values reach Supabase .range().

• parsePaginationParam uses Number() (not parseInt) so mixed strings like "3abc" produce NaN and fall back to the default rather than silently advancing to page 3.
• Three new regression tests verify fractional, non-finite, and mixed-alpha inputs; all expected range() call arguments and response pagination fields are arithmetically correct.

Confidence Score: 5/5

Safe to merge — the change is a narrow, self-contained fix to pagination parsing with no impact on auth, data mutation, or schema.

The helper correctly handles every problematic input class (null, empty, fractional, non-finite, mixed alpha-numeric) through a single, well-ordered chain of Number() → isFinite → Math.trunc → clamp. The new tests directly verify all three regression cases and their expected Supabase range() arguments. No pre-existing issues are exposed by this change.

No files require special attention.

Important Files Changed

Filename	Overview
src/app/api/feed/route.ts	Introduces parsePaginationParam helper that uses Number() + isFinite + Math.trunc + clamping to replace bare Number()
src/app/api/feed/route.test.ts	Adds three regression tests covering fractional, non-finite (Infinity/NaN), and mixed-alpha ("3abc", "7px") inputs; expected range() offsets and response pagination fields are all arithmetically correct.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["GET /api/feed\n?page=X & ?limit=Y"] --> B["parsePaginationParam(value, default, min, max)"]
    B --> C{"value is null?"}
    C -- "yes (??)" --> D["use defaultValue"]
    C -- "no" --> E["Number(value)"]
    D --> E
    E --> F{"isFinite(parsed)?"}
    F -- "false\n(NaN, Infinity, -Infinity)" --> G["return defaultValue"]
    F -- "true" --> H["Math.trunc(parsed)"]
    H --> I["Math.max(truncated, min)"]
    I --> J["Math.min(result, max)"]
    J --> K["clamped integer → feedFiltersSchema.safeParse"]
    K --> L["offset = (page-1) * limit"]
    L --> M["supabase .range(offset, offset+limit-1)"]

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