docs+openspec: prior-art research (Organic Maps, Endurain, wanderer) and 15 proposals

Add docs/inspirations.md as the durable record of the 2026-07-05/06
prior-art research — per-project learnings with source paths, canonical
credit lines, and the changes each spawned — and extend the
acknowledgment lists in philosophy.md/architecture.md (Organic Maps,
Endurain, wanderer).

New OpenSpec changes (proposal/design/specs/tasks each):
- Organic Maps: elevation-profile-hardening, gpx-parser-robustness,
  hiking-time-estimate, poi-index, hiking-foot-profile
- Endurain: account-export, activity-duplicate-review,
  fit-parsing-hardening, activity-locations, self-hosting-guide,
  activity-privacy-controls
- wanderer: federation-hardening, link-share-tokens
- credits-page (user-visible acknowledgments)

Updated in-flight changes with wanderer prior-art sections:
route-federation, route-discovery.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

openspec/changes/credits-page/specs/credits-page/spec.md

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+## ADDED Requirements
+
+### Requirement: Credits page
+The Journal SHALL serve a credits page at `/about/credits` with three sections — inspirations (linked projects with a one-line acknowledgment each, matching the list in `docs/philosophy.md`), data attributions (including "© OpenStreetMap contributors" per ODbL guidelines and, once shipped, GeoNames CC-BY), and key open-source components. All strings SHALL be localized.
+
+#### Scenario: Page renders with inspirations
+- **WHEN** a user (authenticated or not) opens `/about/credits`
+- **THEN** the page lists BRouter, bikerouter.de, brouter-web, Organic Maps, Endurain, and wanderer with links and acknowledgment lines
+
+#### Scenario: Localized content
+- **WHEN** the UI locale is German
+- **THEN** headings and acknowledgment lines render in German
+
+#### Scenario: OSM attribution wording
+- **WHEN** the data section renders
+- **THEN** it contains the canonical "© OpenStreetMap contributors" attribution with a link to the OSM copyright page

openspec/changes/credits-page/specs/legal-disclaimers/spec.md

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+## MODIFIED Requirements
+
+### Requirement: Footer legal links
+Both the Journal and Planner SHALL render a footer with links to Impressum, Datenschutzerklärung, Terms of Service, Credits, and the source repository.
+
+#### Scenario: Footer on Journal
+- **WHEN** a user views any Journal page
+- **THEN** the footer contains links labeled "Impressum", "Privacy", and "Terms" pointing to the respective `/legal/*` pages, a "Credits" link pointing to `/about/credits`, plus a link to the source repository
+
+#### Scenario: Footer on Planner
+- **WHEN** a user views any Planner page
+- **THEN** the footer contains the same legal and credits links, pointing at absolute URLs on the Journal instance (since the Planner is stateless and these pages live on the Journal), plus a link to the source repository