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/hiking-time-estimate/specs/hiking-time-estimate/spec.md

@@ -0,0 +1,44 @@
+## ADDED Requirements
+
+### Requirement: Tobler-based walking time model
+The GPX package SHALL provide a pure walking-time estimator that applies Tobler's hiking function (`speed = 6·e^(−3.5·|slope+0.05|)` km/h) per segment over a sequence of points, using haversine horizontal distance and elevation-derived slope. Segments lacking elevation on either endpoint SHALL be estimated at flat-ground speed. Slope SHALL be clamped to ±100% before applying the formula.
+
+#### Scenario: Flat route baseline
+- **WHEN** a 5 km route with constant elevation is estimated
+- **THEN** the estimate is approximately one hour (flat Tobler speed ≈ 5 km/h)
+
+#### Scenario: Uphill slower than downhill
+- **WHEN** the same distance is estimated once at +20% slope and once at −20% slope
+- **THEN** the uphill estimate is greater than the downhill estimate
+- **AND** both are greater than the flat estimate
+
+#### Scenario: Missing elevation falls back to flat speed
+- **WHEN** a route's points carry no elevation values
+- **THEN** an estimate is still produced using flat-ground speed for every segment
+
+### Requirement: Whole-route estimate in the planner for the foot profile
+The Planner SHALL display the estimated walking time alongside distance and ascent when the active routing profile is the foot profile, computed from the routed geometry's elevation-tagged coordinates. Other profiles SHALL NOT display a walking-time estimate. The display SHALL mark the value as approximate and use localized strings and hours/minutes formatting.
+
+#### Scenario: Estimate shown for foot profile
+- **WHEN** a route is computed with the foot ("Hiking") profile selected
+- **THEN** the sidebar stats include an approximate walking time (e.g. "≈ 4 h 20 min")
+
+#### Scenario: No estimate for cycling profiles
+- **WHEN** the same route is computed with a cycling profile selected
+- **THEN** no walking-time estimate is displayed
+
+#### Scenario: Estimate updates with the route
+- **WHEN** a waypoint is added and the route recomputes
+- **THEN** the displayed estimate reflects the new geometry
+
+### Requirement: Per-day estimates in the multi-day breakdown
+`computeDays` SHALL support opt-in per-day walking-time estimation, populating an optional `estimatedTimeSec` on each day stage such that day estimates sum to the whole-route estimate; callers not opting in SHALL receive unchanged output. The Planner's day breakdown SHALL display each day's estimated walking time when the foot profile is active.
+
+#### Scenario: Day times displayed and consistent
+- **WHEN** a foot-profile route has overnight waypoints splitting it into days
+- **THEN** each day section shows its estimated walking time
+- **AND** the day estimates sum to the whole-route estimate
+
+#### Scenario: Journal call sites unaffected
+- **WHEN** `computeDays` is called without the opt-in (journal route detail)
+- **THEN** day stages carry no `estimatedTimeSec` and existing behavior is unchanged